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280 Cards in this Set
- Front
- Back
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What is charge? |
Fundamental property of the constituents of atoms |
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What is electrostatic forces |
Forces betwen charged particles that are not moving or are moving relatively slowly
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What is columb's law? |
Mathematical relationship that describes the vector force between two small charged objects Mathematical description of the fundamental nature of the electrical forces between charged objects that are small compared to the distance between them |
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What are electric fields used to determine ? |
The net force on a small test charge due to the presence of other charges at different locations |
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How many types of charges are there |
Two types of electrical charge |
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Do like charges repel or attract each other? |
Like charges reel |
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Do unlike charges repel or attract each other |
Unlike charges attract |
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Based on your observations of the movement of the tapes, how does the strenght of these forces compare to the gravitational force on the tapes near the surface of the earth? |
Forces of the tape is reater than the gravitational force since they were able to repel and attract each other instead of just staying vertical (overcome gravity) |
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How does the magnitude of the force betwen two charged objects change as you change the distance between the objects? What happens to the force if you decrease the distance or if you increase the distance? |
Force increases when you decrease the distance Force decreases when you increase the distance |
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Can charged objects exert forces on each other at a distance? |
Yes |
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What do physisicts current bleieve that all contact forces really are |
Electrical forces involving small separations (Physicists believe that all forces act at a distance) |
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What is the equation for the electric field vector (E) is relationship to the force (F) and charge |
E = F/q The electric field vecotr defined as the force (F) that would be experienced by a very small positive charge (test charge) at a point in space, divided by the magnitude of the charge (q) |
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What happened to the metal painted pith ball when the rod was brought near it and then when it was touched |
Like charges repeal each other and unlike charges attract each other. Charges on the metal painted pith ball can move more readily because metals are good conductors. On the other hand, wood is a good insulator so charges do not move as readily. When the rod comes near the metal ball, there is a seperation of charge in which positive charges move towards the side closest to the rod, so there is an attraction However, after both are touched to the rod, the wooden ball was still attracted to the rod; hwoever, the metal ball was repelled by the rod. That is because metal is a good conductor and charges move readily in a good conductor so the negative charges form the rod were transferred to the metal ball. Hwoever, wood is a good insulator and charge does not move easily in an insulator so the charge did not transfer, which is why the wooden ball still attracted to the rod even after touching it |
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One straw floats upon another due to electric force. They have bot hthe same charge. What would happen to the distance of the straws, if the charge on one straw is doubled |
The distance will increase by a factor of square root of 2 |
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One straw floats upon another due to electric force. They have both the same charge. What would happen to the distance of the straws if the charge on both straws is doubled |
The distance will be increased by a factor of 2 |
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You have two charged peices of Scotch Magic tape. How would you determine if they have like or unlike charges? What would you need to determine if they are charged positively or negatively? |
Whether or not they ahve like or unlike charges can be determined by putting the two pieces close to each other. If they repel that means they have the same charge. However, if htey attract that means they have different charges. To determine its charge you need to compare it to an object of a known charge. |
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Two like charges are serparated by some distance. Describe quatitatively what will happen to the force exerted by one charge on the other if the distance between the charges doubled |
Force = 1/4 |
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Two like charges are serparated by some distance. Describe quatitatively what will happen to the force exerted by one charge on the other if the distnace between the charges is halved |
Force = 4x |
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Two like charges are serparated by some distance. Describe quatitatively what will happen to the force exerted by one charge on the other if one of the charges is replaced by a charge of the same magnitude by opposite sign |
The magnitude of force remains the same, but it will be an attractive force |
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What is a battery? |
A device that generates an electric potential difference (voltage) from other forms of energy |
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What do chemical batteries do |
Convert internal chemical energy into electrical energy |
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As a result of a potential difference what happens to electric charge in a battery |
It is repelled from one terminal of the battery and attracted to the other
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Can charge flow out of the battery if there is no conducting material connected between its terminal? |
No |
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What are the conditions needed for the bulb to light? |
Continuous circuit Potential difference |
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Why is the filament of the bulb connected as it is? |
Energy can flow through it and is converted to heat and light The filament also helps to complete the circuit |
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Explain how the bulb socket works. Why desn't the bulb light when it is unscrewed? |
The bulb socket has a metal piece that the metal part of the bubl touches and conducts electricity. When its unscrewed, the conduction cannot occur since metals aren't touching |
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How does current flow through a circuit |
Continuous circuit (in the same direction) and current should be the same throughout the circuit Number of electrons in the circuit are the same |
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If a current sensor measures a + what does that mean? |
Current is goign from the + terminal of the battery and through the - terminal |
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If a current sensor measures a - what does that mean? |
Current flowing into the - terminal and out the + terminal of the sensor |
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How do you determine if an observed difference in the currents ready by sensor 1 and sensor 2 is real or if it is the result of small calibration differences and normal fluctuationsi n the sensor readings? |
Switching the sensors and see if get the same result |
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On the battery symbol, which line represents the positive terminal-the long one or the short one? |
Long one |
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If bulbs are connected in parallel why does all of them not turn off when one turns off |
Because there is the same voltage going through each bulb |
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What is the voltage when the voltage sensor leads are connected to the same point |
Zero |
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What is the voltage when the voltage sensor leads are connected to the two ends on the same wire? |
Zero |
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What is the voltage across a battery when the switch is open and closed |
Constant |
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What is the voltage across a bulb when the switch is open and closed |
Open --> 0 Closed --> same as battery |
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What is the current across the battery as the switch is clsoed or open |
0 when switch is open Constant when switch is closed |
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When you add a second bulb to a one bulb circuit what happens to the voltage? |
Voltage stays constant |
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When you add another bulb to a one bub circuit what happens to the current through the battery? |
Current decreases |
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Is the battery a source of constnat current or voltage |
Voltage (Current is affected by the increased resistence of more bulb) |
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In the picture on page 72 in lab 4, what part of the picture represents the action of the battery? |
Person lifting the ball |
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In the picture on page 72 in lab 4what represents the electric charge and current? |
Movement of the ball |
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In the picture on page 72 in lab 4, what part represents the collisions of the electrons? |
Ball hitting the pegs |
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In the picture on page 72 in lab 4, what ultimately happens to the "energy" given to the balls by the "battery"? |
"Energy" given to the balls by the "battery" is turning potential energy into kinetic energy. This mimics how batteries work in which chemicalenergy is turnedi nto electrical energy and later into heat and light. |
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In the picture on page 72 in lab 4, what plays the role of the bulb |
Pegs in the system |
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How is energy loss exhibited in the circuit you wired that consists of a battery, two wires, and a bulb |
Heat and light |
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How does the model help explain the fact that electric current doesn't decrease as it passes through the bulb? |
Current is defined as charge/time therefore current would be proportional to the v drift. Since the v drift is constant in the image so we know that electric current doesn't decreases as it passes through the bulb and stays constant |
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How does this model help explain the fact taht electrons move with a constant average speed, rather than constant acceleration caused by the constant electric field |
The balls do not get faster because of the collisions with the pegs which explaisn the fact that electrons move with a constant average speed, vdrift, rather than having a constant acceleration caused by the constant electric field (which would have caused the balls to move faster) |
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What happens to the ball current if the drift velocity doubled |
Ball current would double |
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What can you do to the ramp to increase the drift velocity |
Increase the drift velocity, by decreasign the number of pegs (collisions) or increasing the steepness (or general height) of the ramp |
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What is the electric field defined as |
A vector that describes the direction and magnitude of the force xerted on a positive test charge per unit charge |
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What is Gauss' Law? |
Involves relating the electric field surroundign a collection of charges to the net amount of charge inside a closed surface |
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What is the distribution of charge like in Gauss' law? |
Symmetrical |
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How do we represent the electric field in a region of space |
Electric field lines |
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What is the field lines like from going from a +1 charge |
Five lines away from the +1 charge |
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What is the field lines like from going from a -1 charge |
Five lines going towards the -1 charge |
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Are the lines more dense (closely spaced) near the charge? |
Yes |
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How do the directions of thel ines depend on the sign of the charge |
The direction is movign from positive to negative |
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How many lines are in a +2nc charge |
10 lines |
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Describe the rule for telling how many lines will come out of or into a charge inthis simulation. Explain your answer based on your observations. |
When the magnitude of the charges increases, the number of lines also increases in proportion. We saw this because the magnitude of 2nc was 2x more than +1nc and have 2x as many field lines. 10 lives vs 5 lines. These are five lines per unit charge |
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How does the direction of the lines depend on the sign of the charge |
The lines always move from + to - |
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Summarize the properties of electric field lines. What does the number of lines signify? What does the direction of a line at each point in space represent? What does the density of the lines represent? |
The number of lines signify magnitude. Direction of al ine represents the sign of the charge (postive to negative) density of lines represent the strength of electric field |
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How can we think about electric charge |
As having a number of electric field lines diverging from it or converging on it in such a way that the number of lines in proportional to the magnitude of the charge |
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What is electric flux |
Measure of the number of electric field lines passign through a surface |
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What does the number of field lines passign through a surface depend on |
How that surface is oriented relative to the electric field lines |
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By convention where does the normal vector point from |
The outside of the surface |
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What component of the electric field lines contribute to flux |
Parallel
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For angles less than 90 how does flux change |
As angles increase it becomes less parallel and more perpendicular so less and less flux |
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For angles greater than 90 how does flux change |
As angles increase, becomes more and mroe parallel and therefore ahs more and more flux |
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What is the equation for flux through a surface |
flux = (electric field)(area)(cos theta) |
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What is the apparent relationship between the net flux (net number of lines) passing through an imaginary surface and the net charge enclosed by the two-dimensional "surface"? Explain, based on your simulated observations |
Proportional and line of flux equals times q net when the net charge is zero, the net line is zero
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What does Gauss' law state |
Net flux is proportional to the net charge within a closed surface (net flux that pierce) the surface proprotional to the q net it encloses |
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Does an electrical conductor have some of its electrical charges free to move about? |
Yes |
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If a free charge in a conductor experiences an electric field how will it move |
It will move under the influence of that field |
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If a free charge in a conductor experiences an electric field, it will move uner the influence of that field what can we conclude about the electric field |
That if there are no charges moving within a conductor, the electric field within the conductor is zero |
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If a conductor with excess cahrge Q has zero electric field within the conductor, what is the amount of excess charge enclosed by the dashed Gaussian surface? |
Zero since q net enclosed is 0 since no net flux goes through it and the net flux in is the same as the net flux out |
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If the conductor has excess chage and it can't be within the gaussian surface according to Gauss' law, then what's the only place this excess charge can be |
On the surface |
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What can be said about the presence of charge inside of the can? |
There should be no charge on the inside of the can because the charges want to move away from each other as far as they can go, which is the outside of the can. |
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If the total number of lines leaving or converging on a charge doubles, what does that tell you about the magnitude of the charge |
Magnitude doubled |
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What does the density of field lines represent? |
Strenght of the electric field |
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How does Gauss' law explain that excess charge on a conductor must reside on the outside surface |
Gauss' law relates the charge inside the surface to the electric field on the surface. Because the electric field inside a conductor is zero, the charge enclosed by an surface inside the conductor is zero. Gauss' law states that the total of the electric flux out of a closed surface's equal to the charge enclosed divided by the permitivity. Additionally if the cahrge enclosed by any surface inside the conductor must be zero then any excess chage will be trying to move away from one another and therefore end up on the outside surface |
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What are the two kinds of force that dominate our everyday reality |
*The gravitational force acting between masses *Coulomb force acting between electrical charges |
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What is the equation for coulomb force |
F = (k)(q1)(q2)/(r^2) |
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What is the equation for the universal law of gravitation |
F = -G(M1)(M2)/(r^2) |
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Why are electrical and gravitational forces are very similar? |
Since essentially the same mathematics can be used to describe orbital and linear motions due to either electrical or gravitational interactions of the tiniest fundamental particles or the largest galaxies |
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What is different about the force laws |
Gravitational force i always attractive and electrostatic force can be either attractive or repulsive
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What part of each equationdetermines whether like charges or masses are attractive or reulsive |
Can't figure out from the equation |
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Is the gravitational or electric force larger |
Electrical force is larger |
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What increases the gravitational potential energy of the object |
Taking work to lift an object under thei nfluence of the Earth's gravitational force |
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What is a conservative force
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Work required to move an object under the influence of the gravitational force is path independent |
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What is two equations to find work |
(f)(d)(cos theta) (q)(E)(cos theta) W = -PE |
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When moving a charge perpendicular to the electric field what is the work done by the field on the charge? |
0 (cos 90 = 0) |
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What is an equipotential surface in terms of work |
If an electric charge can travel along a surface without any work being done, the surface is defined as an equipotential surface |
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What is the relationship between the direction of the equipotential lines and direciton of the electric field |
Perpendicular |
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The patterno f potential differences can be related to what |
The electric field caused by the charges that lie on the conducting surfaces |
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waht are the similarities and differences between the equipotentials for the "point" electrodes and line electrodes |
Point electrodes are circular and line electrodes are almost straight horizontal lines by slightly bulged out |
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Describe the simialrities and differences between the field lines for a "point" electrodes and those for the line electrodes |
Field lines are football shaped for point electrodes and vertical lines for line electrodes but slightly bulged out a bit in places |
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What are capacitors used for |
To store charge and/or energy or to trigger a timed electrical event |
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How do you transfer the equal and opposite charges to the plates of a capactior |
Use a battery or power supply to produce a potential difference between the two conductors Electrons will then flow form one conductor (leaving a net positive charge) to the other (making its net charge negative) until the potential difference produced by the two conductors is equal to that of the battery |
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What is the equation for the capacitence of the capacitor |
C = q/v |
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What is capacitence |
Measure of the magnitude of the net or excess charge on either one of the conductors per unit potential differnece |
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What type of excess charge will build up on the metal plate that is attached to the negative terminal of the battery |
Negative |
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What ty[e of excess charge will build up on the plate that is connected to the positive terminal of the battery
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Positive |
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Can the excess positive charges on one plate of a charged parallel-plate capacitor exert forces on the excess negative charges on the other plate? |
Yes, because the difference in potential produces an electric force, which produces a force |
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If the area of the capacitor of the plates were increased, what do you think would happen to the amount of excess charge on each othe plates |
Increase, because amount of excess charge that plate can accumulate |
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How does capacitence change will you increase area |
Increase (C = q/V and q is increased) |
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If the battery is then disconnected what do you think woudl happen to the potneital difference between the plates if the seperation d were decreased with the excess charge on each plate held constant |
Decrease, because decrease in seperation reulsts in an increase in capacitence and electric field increases |
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What is the equation for capacitence? |
C = (epsilon0) (A)/distance) |
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What is the relationship between capacitence and distance |
Inversely proportional
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Why was our capacitence off by a magnitude of 10 |
Because we assuemd the permativity of the book is the same as air which i not true |
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What is the relationship between equipotential surfaces (or lines in two dimensions) and the direction of electric field lines? |
Equipotential lines in order to require zero work, must always lie at a 90 degree angle or perpendicular to the electric field lines. |
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How much work is done moving a charge along an equipotential surface (line)? Explain. |
Zero work is done When looking at work we want to calculate W =Fd using parallel componenets to the electric field. However, since equipotential surfaces are perpendicular to the electric field, no work can be done, since no componenet is parallel to the electric field. Also as moving along an equipotnetial line, potential energy is not changing at all, so delta PE = 0 and if W = -PE then W =0 as well. |
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Explain how you would use a voltmeter to find equipotential lines for electrodes painted on carbonized conducting paper with conducting paint |
You would put a charge along the electrical point then measure voltages at points on the paper. You would connect spots that have the same voltages which would give the lines or curve along which there are no change in PE. These are equipotential lines
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How would you draw in the electric field lines once you located equipotential lines on the carbonized conducting paper? |
Draw in perpendicular to the equipotnetial lines going from positive to negative |
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Is there any difference between the static charges generated by rubbing rods with fur or silk and the charges that flow (from a battery) through wires in an electric circuit? Give evidence for your answer. |
Charge by each method are the same |
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For a circuit with one bulb and a circuit with two bulbs in series, what is the voltage across the battery for each one |
Should be the same because the battery is made with a difference in potential, the voltage that allows the urrent to flow. Therefore, a charged battery matintains a constant voltage as we have seen. |
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In order to cause current to flow through a bulb what do you need |
You must have a complete circuit that includes a voltage source such as a battery and also a complete path from the positive terminal of the battery, through the connecting wire to the bulb, though the bulb, through the connecting wire to the negative terminal of the battery |
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Is the electric current the same in all parts of the circuit? |
Yes |
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Does a fresh battery maintain essentially the same voltage whether it is connected to one light bulb or two? |
Yes |
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Is current smaller or larger when a second bulb was added to the circuit? |
Smaller |
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What determines how much current is provided by the battery? |
Total resistence of the elements in the circuit determines how much current is provided by the battery |
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What is the relative brightness of the three bulbs, A, B and C |
A> B=C |
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What will happen to the brightness of bulbs A, B and C if the battery is connected to the bulbs with its terminals reversed? |
Brightness is still A > B = C because current is still flowing from positive to negative |
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Can you tell the direction of current through a circuit by looking at the brightness of the bulbs without knowing how the battery is hooked up? |
No
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Are the currents flowing into and out of bulb A equal? What about the direction of the currents? |
Equal |
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What is the direction of current flowing through bulb A? |
From positive to negative (only 1 direction) |
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For the circuit with two bulbs, is current "used up" in the first bulb, or is it the same in both bulbs? |
The current was the same because the current is not used up by one bulb and is constant throughout the circuit. It was less than a one bulb circuit |
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How is the brightness of a bulb related to the current flowing through it? |
Brightness of a bulb is directly proportional to current flowing through it |
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What is the relative ranking of current flowing through each resistor |
A > B = C |
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Why is the current through the resistors directly inversely proportional to resistence while bulbs were not exactly the same |
Because a resistor is an ohmic device and a bulbs are not |
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What does series connection mean |
Two resistors are in series if they are connected so the same current that passes thorugh one passes through the other |
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What does parallel connection mean |
Two resistors are in parallel if their terminals are connected so that at each junction one terminal of one resistor is directly connected to one terminal of the other |
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What is the current like through D when switch is open and closed |
Constant |
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What is the current like through C when switch is open and closed |
Open = 0 Closed = Same as D |
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What is the current like through the battery when the switch is open and closed |
When switch open, current is the same as current through D Closed = Current is D +E 's currents |
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What is a rule to predict how the current flowing through a battery will change as the number of bulbs conencted in parallel increases. Can you explain why? |
The current though a battery is proportional to the number of bulbs connected in parallel. It increases as bulbs increase because the battery has to provide the same current to each bulb. The current out of battery has to increase in order to pump more current to feed the additional bulbs. |
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Does adding more bulbs in parallel increase, decrease or not change the ottal resistance of the circuit |
Decreases |
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Why does adding more bulbs in parallel decrease the total resistance of the circuit in terms of number of paths for current available in the circuit |
Number of pathways for current to travel increases, which helps to decrease the total resistance of the circuit |
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Does current flowing through a battery depend only on the number of bulbs or resistors in the circuit, or does the arrangement of the circuit elements matter? |
Arrangement plays a crucial role as well |
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In b is bulb A in series with bulb B? with bulb C? or with a combination of bubls B and C? |
Combination of bubls B and C |
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Are bubls B and C connected in series or in parallel with each other in (b) |
In parallel because the current splitsequally to bubls B and C and are seperated by junctions |
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Is the resistance of the combination of bulbs B and C larger than, smaller than or the same as bulb B alone? Explain. |
Smaller, because the parallel orientation decreases the contribution of resistence each bulb in parallel makes to the circuit, since 1/Req = 1/R1 + 1/R2 + ... |
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Is the resistance of the combination A, B and C of b larger than, smaller than or the same as the combination of A and B in a? |
Smaller |
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What happens to the current flowing through the battery and through bulbs A and B and when bulb C is added in parallel with bulb B? What do you conclude happens to the total resistance in the circuit? |
The current increases as a result of adding the bulb C in parallel to bulb B. Bulb A had more current flowing to it, while current through bulb B decreased because the current is evenly distributed between bulb B and C so despite the fact that the overall current increased. This increase in current shows that the resistance dropped. |
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When switch S is open, which bulbs are connected parallel with each other |
A parallel to the combination of B and C |
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When switch S is open, which bulbs are connectedi n series with each other |
B and C |
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When switch S is closed, which bulb(s) are connected in parallel with A? |
The combination of B with (D and C) together is in parallel with A |
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When switch S is closed, which bulb(s) are connected in series with B |
B is in series with the combination of D and C |
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What happens to the current flowing hrough bulb A when you unscrew bulb B |
No effect |
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What happens to the current flowing through bulb A, closing switch S |
No effect |
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What happens to the current flowing through bulb B when you unscrew bulb A |
No effect |
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What happens to the current flowing through bulb B when you add another bulb in series with bulb A? |
No effect |
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Rank the five circuits by total resistence |
5>2>1>4>3 |
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Rank the five circuits by the total current flowing through the battery |
3>4>1>2>5 |
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What is the ranking of relative brightness of each of the bulbs |
E > A = B > C = D (Reasoning lab 5 page 96) |
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Which of the three circuits shown are the same electrically? |
1 = 2 = 3 |
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Which circuit diagram corresponds to circuit 1? |
B |
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Which circuit diagram matches circuit 2? |
D |
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Which circuit is not like the others |
Circuit C because it is connected in sereis while all the others are in parallel formation |
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What is the circuit diagram for A? |
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What is the circuit diagram for B? |
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What is the circuit diagram for C? |
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What is the circuit diagram for D? |
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Rank resistors from largest to smallest |
C > E > A > B > D |
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If a battery were connected to each of the circuits in Question 4, in which network would the current flowing through the battery be the largest? The smallest? |
Largest = D Smalest = C |
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The diagram below shows a typical household circuit. The appliances (lights, television, toaster, etc) are represented by boxes labeled 1, 2, 3 and so on. The fuse, or circuit breaker, shown in the diagram is a switch intended to shut off the circuit automatically if the wires become too hot because the current flowing in the circuit is too large. What happens to the current flowing through the fuse when more appliances are added to the circuit? Describe evidence from this lab for your answer |
Current will increase. More parallel branches, more pathways for current to travel and thus more current through the fuse |
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The diagram below shows a typical household circuit. The appliances (lights, television, toaster, etc) are represented by boxes labeled 1, 2, 3 and so on. The fuse, or circuit breaker, shown in the diagram is a switch intended to shut off the circuit automatically if the wires become too hot because the current flowing in the circuit is too large. Does the current flowing through element 1 change when elements 2 and elements 3 are added to the circuit |
The current passign through element 1, 2 or 3 is independent of the other elements. Thsi was seen in Activity 2-2, when the current passing through bulb D was the same whether it was attrached to bulb E or not. So it will not change |
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The diagram below shows a typical household circuit. The appliances (lights, television, toaster, etc) are represented by boxes labeled 1, 2, 3 and so on. The fuse, or circuit breaker, shown in the diagram is a switch intended to shut off the circuit automatically if the wires become too hot because the current flowing in the circuit is too large. Is the model consisstent with your observations of everyday household electricity. For example, what happens to the brightness of a light bulb in a room when a second one is turned on? |
Yes when one light is turned off, it doesn't appear to affect the brightness or currents of other lights, which is what we observe in everyday household electricity |
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The diagram below shows a typical household circuit. The appliances (lights, television, toaster, etc) are represented by boxes labeled 1, 2, 3 and so on. The fuse, or circuit breaker, shown in the diagram is a switch intended to shut off the circuit automatically if the wires become too hot because the current flowing in the circuit is too large. What may happen to the fuse if too many appliances are added to the circuit? Why? |
Current become so large that the fuse becoems hot and blows out |
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Are the bulbs C, D, and E connected in series, parallel or neither? |
Parallel |
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Rank the bulbs in order of brightness. Use the symbols =, <, and >. |
A = B > C = D =E |
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How will the brightness of bulbs A and B change if bulb C is unscrewed? Will the result be different if bulb D or E is unscrewed instead? |
Decrease slightly because when you unscrew C or D or E, the resistance across C/D/E will increase since there is less pathways to take and that will cause the voltage to consume to increase and since voltage across the battery is not changing so voltage across A/B will decrease making them less bright than before. |
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Rank bulb brightness |
A > B > C > D = E |
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In the two circuits below, the batteries and all bulbs are identical. Compare the current flowign in the circuit on the left to the current flowing in the circuit on the right. Be as quantitative as possible |
The current flowing in circuit A will be higher than that is circuit B since circuit B has three times the resistance. Is not a direct relationship though just because it is not ohmic |
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Compare the current flowing in the circuit to the left to the current flowing in the circuit on the right. Is your answer the same as with bulbs? |
Circuit A will have a higher current than in circuit B and circuit B will have 1/3 of the current compared to circuit A. These resistors, however, are ohmic, which means that since circuit B has 3 x as much resistance as A it will have 1/3 of the current as A. While both bulbs and resistors are inversely proportional. The ohmic resistors have a direct relationship between the number of reistors and the amount of current passing throug hthe circuit, while bulbs are not perfectly proportional which is how it differs from question 9 |
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For a series circuit what is the current like |
The same current flows through all elements |
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For a parallel circuit, what happens to current |
Current divides among the branches so that the ottal current flowing through the battery equals the sum of the currents flowing through each of the branches |
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When two or more parallel branches are connected directly across a battery, does making a change in one branch affect the current flowing in the other branches |
No |
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Does changing one part of a series circuit affect the current flowing in all the parts of the series circuit? |
Yes |
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What does the potential difference across two bulbs in series equal to? |
The voltage of the battery |
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What happens to the potential difference across the battery when you close the switch? |
Stay the same becaue the voltage across a does not affect the voltage across B |
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What is the voltage across bulb A when switch is open and closed |
Constant (same as voltage across battery) |
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What is the voltage across bulb B when switch is open and closed? |
Switch open: 0 V Switch closed: Same as voltage across bubl A |
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The total voltage across each branch in a parallel circuit is equal to what |
The voltage across the battery |
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Is a fresh battery a constant current source or a constant voltage source |
Constant voltage source |
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What is the voltage between two points on a short lenght of wire when there is no bulb, battery, or resistor between the points
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0 V Becase it is an equipotential wire and there is no difference in charge |
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How did voltage change as you closed more switches |
Voltage decreased |
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How did current change when you close more switches |
Current increases |
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Why did current increase and voltage decrease as closing more switches |
As you close more switches, you need more current to go throug hthe circuit; however, from the diagram since the resistance of the battery stays the same and current is increasing so from V = IR, the battery will be consuming a greater and greater amount of voltage and so there will be a greater voltage drop with more switches closed through the circuit |
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When you close the switch what happens to the brightness of bulb B? |
Decrease |
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What is a DC power supply like? |
A variable battery. When you turn the dial, you change the voltage between its terminals |
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What happesn to the current flowing through the resistor as you turn one the power suppy and increase the applied voltage from zero |
Current increase due to a higher difference in potential |
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How does the potential difference across the resistor change as the current flowing through the resistor change
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Potential difference increased as current increased They are proportional |
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In words, what is the mathematical relationship between potential difference and current for a resistor? |
Directly proportional R = V/I |
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What is the value of R for a resistor- is it constant, or does it change as the current flowing through the resistor changes |
Constant |
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What happened to the brightness of the bulb as the power supply voltage was increased? |
Getting brighter |
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How is the brightness of the bulb related to the potential difference across the bulb? To the current flowing throug hthe bulb? |
Brightness increases at a similar rate to the potential difference and current flowign through a bulb, but is not directly proportional |
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What is the graph for the voltage vs current |
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Is the value of R for a bulb-constant or does it change as the current flowing through the bulb changes |
Changes Resistence increases as a bulb gets warmer so it is not constant |
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Is a light bulb an ohmic device? |
No |
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How do the brightness of the three bulbs compare to each other? |
A > B = C |
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What happens to the brightness of each of the three bulbs when bulb A is unscrewed and removed from its socket? |
A not lit B and C are not affected Because current running through the B and C branch is unaffected by the A branch |
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When A is unscrewed what happens to the current through points 3, 4 and 5? |
Current thorugh 3 will decrease since A is no longer drawing current so overall current through the battery will decrease Current through 4 will not change since current in that branch not affect Point 5 is 0 |
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Bulb A is screwed bakc in. What happens to the relative brightness of each of the three bulbs when bulb C is unscrwed and removed form its socket |
C and B not lit A not affected |
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When C is unscrewed what happens to the current flowing through points 3, 4 ,5? |
3 decrease Point 5 not change 4 is 0 |
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For each of the questions A-E below, a wire is connected from the battery terminal at point 1 to point 4 What happens to the brightness of each of the three bulbs? |
A stays same B not lit C brighter |
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For each of the questions A-E below, a wire is connected from the battery terminal at point 1 to point 4 What happens to the current flowing through point 3? |
The current will decrease because they were in series and now they are in parallel |
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For each of the questions A-E below, a wire is connected from the battery terminal at point 1 to point 4 What happens to the potential difference across bulb B |
0 |
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For each of the questions A-E below, a wire is connected from the battery terminal at point 1 to point 4 What happens to the potential difference across bulb C |
Increase |
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For each of the questions A-E below, a wire is connected from the battery terminal at point 1 to point 4 What happens to the potential difference between points 1 and 5 |
There would be no change in potential since the difference in potential at point 5 is that of the battery because the potential at point 5 is still 0 |
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Wat happens to the brightness of each of the three bulbs and to the current flowign through point 2 if a wire is connected from the battery terminal at point 2 to the socket terminal at point 5 |
Potential difference is zero so does not change |
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If a fourth bulb (D) is connected to the circuit parallel with bulb B. What happens to the brightness of the three bulbs? |
Bulb A same Bulb B decrease Bulb C increase |
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If a fourth bulb (D) is connected to the circuit parallel with bulb B. What happens to the current flowing through point 3? |
The current will increase since the resistance of the first branch decreased, so it will draw more current |
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If a fourth bulb (D) is connected to the circuit parallel with bulb B. What happens to the potential difference between points 3 and 4? |
Decrease Less resistance, less voltage drop though B and D in parallel |
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If a fourth bulb (D) is connected to the circuit parallel with bulb B. What happens to the potential difference between points 4 and 2? |
The potential differene will increases since now that bubl C has higher current flow, it will pass more current though it. Tbhs the voltage through bubl C from before it at point 4 to after is at point 2 will be greater |
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State Ohm's law in words |
The voltage of the circuit is equal to the product of its total current and total resistance. Thus it relates voltage, current and resistance especially resistors that are metal conductors |
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Does a light bulb have a constant resistance |
No, resistance of light bulb fluctuates with changes in temperature |
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Is the resistors are connected in series, which are connected in parallel, and which are neither in series nor parallel |
Series |
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Is the resistors are connected in series, which are connected in parallel, and which are neither in series nor parallel |
Parallel |
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Is the resistors are connected in series, which are connected in parallel, and which are neither in series nor parallel |
A and D are in series B and E are in sereis AD and C and BE are in parallel |
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Is the resistors are connected in series, which are connected in parallel, and which are neither in series nor parallel |
BC are in parallel A and BC are in series |
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In a series connection of capacitors, how many paths are there for charge
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One Whatever charge is placed on one of the capacitors must be transferred to theo thers |
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What are the connections like for a parallel connection of capacitors |
Two terminals of each capacitor are connected directly to the terminals of the others Each capacitor defines a branch, so the total charge transferred to the capacitor combination is divided among the difference capacitors |
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What is the general equation for the equivalent capacitance for parallel network of capacitors |
C eq = C1 + C2 + C3 +... |
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What is the general equation for the equivalent capacitence for series network of cpacitors |
1/Ceq = 1/C1 + 1/C2 + ... |
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Draw a sketch of the approximate brightness of the bulb as a function of time for the above case where you move the switch to position 1 after it has been in position 2 for a long time. |
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After the above one, now move the switch back to position 2. draw a sketch of the approximate brightness of the bulb |
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Why does the bubl behave that way. |
While in position 1, the potential across the capacitor increases until its voltage is equal to that of the battery. When switched to 2, the battery is discharged and the voltage sotred in the capacitor is released to produce a current which has the same brightness both times |
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What is the equation that represents voltage v(t) across the capacitor as a function of time |
v(t) = V0 e^ (-t/RC) |
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How calculate the time constant |
Resistance * capacitence |
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Explain in terms of the charge, electric field and potential difference how the capacitence of a parallel-plate capacitor depends on the area and separation of the plates in the equation C = (E0)(A)/d |
When the area increases, there is more space charges can accumulate, so the potential difference decreases and the electric field decreases according to C = Q/V = Q/(E*d). When the seperation decreases, the electric field is stronger and capacitence
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If a 1.5 V battery is connected to a 250 microF capacitor, how much excess charge is there on each of the capacitor plates |
Q = CV = 3.75E-4 C |
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For a circuit with two capcitors in series indicate whether the statement is TRUE or FALSE, and for each false statement, write a correct one Both capactiors have the same amount of charge on their plates |
True |
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For a circuit with two capcitors in series indicate whether the statement is TRUE or FALSE, and for each false statement, write a correct one The voltages across the capacitors are the same |
Flase, voltage across the capacitors are not the same because the voltage adds up capacitors are in sereis |
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For a circuit with two capacitors in series indicate whether the statement is TRUE or FALSE, and for each false statement write a correct one The sum of the voltages on the two capacitors equals the voltage of the battery |
True
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Find Ceq |
8.57 microF (Page 163 Lab 8) |
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Find C eq |
8.57 microF |
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Find Ceq |
100 microF |
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Describe what is observed when the switch is closed |
The bulb will be lit for a few seconds and then get dimmer and dimmer slowly until it goes out
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How would your observations be changed if the capacitor were twice as large |
Bulb will be lit for a longer time period before it dies off |
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How would your observations be changed if the bulb had half as much reisstance |
Bulb twice as bright then gets dimmer and turns off in a shorter time |
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In this circuit, the capacitor is initially charged. If it has capacitor 0.023 F, and te reisistor has reistance 47 ohms, how long after the switch is closed will it take for the voltage on the capcitor to fall to 37% of its initial value? |
t = 1.07 sec |
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Do magnets exert forces on each other? |
Yes |
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Electric currents that are caused by electric fields can cause _______ |
magnetic effects |
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Permanent magnets can exert ______ on current-carrying wires and vice versa |
Forces |
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Electric currents can produce |
Magnet fields |
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Changing magnetic fields can produce ____ |
Electric fields |
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Can you find a magnet with just a north pole or just a south pole? |
No |
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Can u find unlike electrical charges separately? |
Yes |
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Does a magnet attract a aluminum rod? |
No |
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What orientation would a suspended magnet orient itself with another magnet |
Antiparallel |
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What does the north pole of a magnet align with |
North direction whichi s the south magnetic pole |
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If the suspended magnet still appears to orient itself, what might be underneath the room. |
Earth has a north pole and a south pole,. We are on Earth so the orientation would still happen outside. Eart's magnetism exists under the ground |
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What does the compass needle compose of |
Magnet bcause it detects the Earth's magnetic poles and positions itself to orient antiparallel |
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The North pole on Earth attracts _____ pole on the magnet. What is the magnetic pole it is |
North pole on the magnet It is a magnetic south pole |
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What is the relationship between amgnetic field and distace |
Magnetic field decreases as distance increases |
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When you have a magnet attached to a paperclip and attract another paperclip with that paperclip is the paperclip being attracted to the magnet or the other paperclip? |
Other paperclip Paperclips are ferromagnetic (and has magnetic domains) but with a strong enough magnetic field can let magnetic domains align so can become magnetic (Magnetization) |
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When is the effect of magnetization stronger? |
When the object is placed in a stronger magnetic field |
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How does magnetization hapen |
Electrons behave like tiny magnets Unpaired electrons like to point in the same direction, if they are placed in a srong magnetic field, these tiny paired electrons act together and become a strong magnet |
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Are magnetic attractions the same as electrostatic attractions |
No
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What happens when the speed of the electrosn is increased |
Force increase So bends more |
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What happens to the distplacement of the electrons when the magnetic field strength is incred |
Higher displacement and more bending |
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What is the equation of force for magnetic force |
F = q v B (Lorentz force equation) |
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Is the equation for magnetic force sine or cos dependent |
Sine because needs to be perpendicular |
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Permanent magnets can exert forces on what |
Freely moving charges and on electric currents in conductors |
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What does Newton's Third Law state? |
Whenever one objets exerts a force on another object, the second object exerts an equal and opposite force back |
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Do currents and moving charges produce magnetic fields themselves? |
Yes |
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What is the RHR for determining the direction of the magnetic field on a current carrying wire |
Thumb in the direction of current Fingers bend in direction of magnetic field |
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How does field strength vary as you move away from the wire? |
Decrease |
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Does field vary in the same way on both sides of the wire |
Yes |
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How should the sensor be held? |
So that field lines are perpendicular to the faceW |
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What happens to the strength of the magnetic field at a given distance from the wire when the current in the wire is decreased |
Strength decreases |
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What do you think is responsible for inducing electrical effects in a coil of wire, the presence of a magnetic field or the presence of changing magnetic field |
Presence of changing magnetic field |
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What is the equation for magnetic flux |
(B)(A)(Cos theta) |
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What are the three ways to produce a changing magnetic flux through the surface of a coil |
Magnetic field strenght (thorugh distance) Area of the coil Angle between area and magnetic field |
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What gives you a larger margnitude, moving the magnet slower or faster? |
Faster Change in flux is same but rate of change is greater Therefore, induced emf depend on the rate of change of flux I |
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s there an induced emf when rotating the magnet? |
Yes, because the amount of magnetic field lines it captures changes |
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What is Faraday's Law |
Magnitude of the induced emf across a conducting coil with N turns is equal to N times the negative rate of change of the magnetic flux passing through the area enclosed by the coil (Equation on page 203 of lab 10) |
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What is change in flux |
Final flux - initial flux |
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What happens to the absolute value of the rate of change of the lfux, through the coil if the magnet is moved more rapidly through the coil? |
Increases |
