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48 Cards in this Set
- Front
- Back
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Explain how objects can become charged by induction. |
- When you rub an object e.g. a balloon against e.g. your hair, friction causes electrons to be rubbed off from the atoms in your hair onto the balloon. - Because the balloon gains electrons, it gets an overall negative charge. |
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Explain how balloons cause hair to become attracted to them. |
- Friction: after friction occurs, the balloon is charged by induction - Repel: the electrons in the balloon repel the electrons in the hair (protons stay still) - Attract: electrons in the balloon are attracted to the protons in the hair - hair moves towards balloon |
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What are the charges of protons, neutrons and electrons? |
Proton: +1 Neutron: 0 Electron: -1 |
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What are the masses of protons, neutrons and electrons? |
Proton: 1 Neutron: 1 Electron: Negligible (0.0005) |
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What is the process of earthing and discharge? |
- When you build up an electrostatic charge e.g. by walking on carpet, you feel an electric shock when you touch a metal object (e.g. doorknob). - Electrons flow through you to the object to the earth - You no longer have a charge |
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How is lightning formed? |
- Static electricity builds up on clouds and causes a huge spark to form between the earth and clouds. - Lightning we see is caused by charged particles flowing through the atmosphere |
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What are bonding lines and how and why are they used? |
- They connect aircraft to the earth before being refueled - Static electricity can build up as fuel flows through a refueling pipe, and it can also build up as aircraft move through the air - Bonding lines discharge the craft so there are no sparks |
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List two of the dangers of static electricity. |
- Lightning - Refueling aircraft |
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Describe how static electricity can be used. |
Electrostatic spray painting - Metal spray nozzle gives paint droplets + charge - + charged droplets repel - spread out into fine spray - Object given a negative charge - Droplets attracted to object's surface |
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Describe how electrons are distributed when a cloth is rubbed against a metal rod. |
Since metals conduct electricity, the extra electrons spread themselves out through the metal. |
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Describe how electrons are distributed when a cloth is rubbed against a polythene rod. |
The electrons transferred from the cloth can't move so the end of the rod has a static charge. |
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Define current. |
The rate of flow of charge. |
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What is a direct current (DC)? |
A type of current where the current flows in one direction. |
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What is an alternating current (AC)? |
A type of current where the electrons change direction many times each second. |
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What are the units for charge? |
C (Coulombs) |
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What is the formula for charge? |
Q = I x t Charge (C) = Current (A) x Time (s) |
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Complete the sentence: In a series circuit, the current _______ |
In a series circuit, the current is the same in all positions |
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Complete the sentence: In a parallel circuit, the current _______ |
In a parallel circuit, the current splits at the junction and takes the path of least resistance |
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Complete the sentence: In a series circuit, the voltage ________ |
In a series circuit, the voltage of the components adds up to the voltage of the cell/supply |
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Complete the sentence: In a parallel circuit, the voltage _______ |
In a parallel circuit, the voltage is the same in each branch |
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What is the formula for Ohm's law? |
V = I x R Voltage (V) = Current (A) x Resistance (Ohms) |
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What is resistance? |
It's what opposes the current flow. |
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How are resistance and current related? |
They're in inverse proportion. When there's more resistance, there's less current (and vice versa) |
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Describe how the heat and resistance of filament lamps change depending on usage. |
More use = more heat More heat = more resistance |
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True or false: diodes conduct electricity in only one direction. |
TRUE |
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How does light affect resistance and current in an LDR (Light Dependent Resistor)? |
Light: UP Resistance: DOWN Current: UP |
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How does temperature affect resistance and current in a thermistor? |
Temperature: UP Resistance: DOWN Current: UP |
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Why does current cause heating? |
- Electrons collide with ions in conductor - Collision transfers energy to ions - Ions vibrate more - Temperature rises |
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What are the formula for power? |
P = I x V Power (P) = Current (A) x Voltage (V) P = E/t Power (P) = Energy (J)/Time (s) |
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What is the formula for electrical energy? |
E = I x V x t Energy (J) = Current (A) x Voltage (V) x Time (s) |
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What is the formula for speed? |
V = d/t Speed (m/s) = Distance (m) / Time (s) |
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What is the displacement? |
The distance between the start and finish in a straight line |
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What does velocity tell you? |
The speed and direction in which something is moving. |
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What are vector quantities? |
Quantities with a size and direction |
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What is the relationship between speed and gradient on a distance-time graph? |
Gradient = speed |
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What is the formula for velocity? |
V = displacement/time |
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How would you calculate the distance based on a velocity-time graph? |
You'd divide the sections into shapes e.g. rectangles and triangles, and find out their individual areas. Then, add them together. |
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Define acceleration. |
The rate of change in velocity. |
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What is the formula for acceleration? |
a = (v-u)/t Acceleration (m/s(2)) = change in velocity/time (s) |
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What is Newton's First Law? |
An object will remain at rest or at a constant speed in a straight line if the forces on it are balanced. |
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How do you work out the resultant force? |
You calculate the difference between the weight and reaction (force pushing against the weight, normally upwards) |
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What will the arrows look like on a free body diagram if all the forces are equal? |
The arrows will be of an equal size. |
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What is Newton's Second Law? |
An object with an unbalanced or resultant force on it has an acceleration in the direction of the force (f:ma) |
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What is deceleration and how is it caused? |
- Negative acceleration, or slowing down - When there's a resultant in the opposite direction of the velocity, this causes deceleration |
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What is Newton's Third Law? |
Every action has an equal and opposite reaction. |
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What is the formula for force? |
F = m x a Force (N) = Mass (kg) x Acceleration (m/s(2)) |
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Define terminal velocity. |
A constant, maximum velocity reached by object falling. This happens when weight downwards is not equal to air resistance upwards. |
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What is air resistance proportional to? |
Speed |
