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55 Cards in this Set
- Front
- Back
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What is a cathode ray beam?
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A stream of electrons
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What is thermionic emisssion?
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The emission of charged particles from a surface due to the addition of thermal energy.
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a) What is this called?
b) What are some things it was used for? |
a) Cathode Ray Tube
b) Television screens, Computer screens, cathode ray oscilloscope (looking visually at waves that normally can't be seen with the eye), x ray tubes, |
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What are each of the elements?
What extra element should be added if this were used for a television screen? |
In order from left to right:
1) Cathode (filament) 2) Anode 3) Y plates X plates which would be in the plane of the screen. |
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What is the purpose of the cathode and the anode in this picture?
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Give the electron kinetic energy after it has escaped the surface of the filament (through thermionic emission).
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What is the purpose of the y plates in a cathode ray tube?
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Move the electron beam up and down.
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A relay uses what type of force to close a switch?
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magnetic
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What is the most common purpose of a relay switch?
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allowing a small current to switch on a large current
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What type of particles does a cathode ray tube fire?
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electrons
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On the right there is a device with a blue circle. What is it called? What is it's function?
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A transistor, it acts as a switch when enough current is passed through the base.
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What is the yellow rectangle on the right? What is it's function?
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A magnetic relay. It acts as a switch for another circuit.
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Identify the following:
D1 R3 VR1 What determines the resistance in each? |
D1 - Diode (The direction of the current)
R3 - Thermistor (Temperature - low T = high R, low I. high T =low R, high I VR1 - Variable Resistor (a minion putting it at a resistance) |
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What is this?
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Minion!
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What is this showing?
What will happen when the blue switch is closed? |
An electromagnetic relay switch.
The bell will ring. |
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What does AC mean, and why is it necessary to have it in that circuit?
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Alternating Current.
Because the relay only closes the switch, but the bell still needs electrical energy to function. |
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Considering C and D, which is positive and which is negative?
How could you lessen the deflection of the electron beam? |
D is positive, C is negative.
Lower the potential difference across C and D |
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What are A and B?
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A is a cathode
B is an anode. |
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Draw the electron beam path through the charged plates, and several cm after it leaves the charged plates.
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Make sure to show that the path is CURVING towards the positive plate while in between the plates and travels in a straight line after leaving the plates.
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a) What is this?
b) What does the y axis measure? c) What does the x axis measure? |
A cathode ray oscilloscope
The amplitude of the signal Time |
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The time setting on this CRO is 10ms for every 1cm.
What is the time period of this wave? What is the frequency? |
T = 40ms = 4.0 x 10^-3s
f =1/T=250 Hz |
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The voltage setting on this CRO is 10v for every cm.
What is the maximum voltage for this signal? |
10v
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The spot on this screen takes 5.0ms to move 1.0cm horizontally.
How long does it take for one cyle? What is the frequency? |
20.0ms (Time period)
f=1/T=1/.02=50Hz |
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Draw a cathode ray tube. Label the most important components.
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need to complete
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What is inside a cathode ray tube?
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Nothing but electrons and the components... no air. Vacuum.
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Where will you see glowing in a cathode ray tube?
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Where a phosphor coated screen is. Typically this is at the end and the screen is perpendicular to the electron beam, but in the example we saw in class the screen was along the beam of electrons.
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a) Which component directs the beam up and down?
b) Which component directs the beam left and right? |
a) The y plates
b) The x plates |
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A) What is the name of this device?
B) Where would you put the arrow if you want the voltmeter to measure voltage of the battery? C) Where would you put the arrow if you want the voltmeter to read zero? |
A) Potentiometer.
B) Above the potentiometer? C) Below the potentiometer. |
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Identify the logic gates from left to right
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2 Not gates, 2 and gates, an or gate.
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a) What is the name of the logic gate and what does it do?
b) What is the name of the device opposite the heater? |
a) NOT gate, reverses the state of input. If input is high (1), output is low (0), if input is low (0), output is high (1).
b) Thermistor |
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Explain how this circuit will work in high temperatures and low termperatures?
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High Temperatures: When the temperature is high, the resistance along the thermistor is low, which means the current through the thermistor is high, making the current input in the NOT gate low, which the output of the not gate is then High
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1 / input sensor
2 / processor 3 / relay 4 / output device |
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When the switch S is closed, the relay acts as a . . . . . 1 . . . . . .
A small current flows through the . . . . . 2 . . . . . in the relay. This closes the contact in the . . . . . 3 . . . . . . Now a large current can flow through the . . . . . 4 . . . . . . |
1 / switch
2 / coil 3 / relay 4 / lamp |
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The capacitor stores . . . . . 1 . . . . . .
When the switch is closed, a . . . . . 2 . . . . . flows in the circuit. The . . . . . 3 . . . . . across the capacitor increases. If the . . . . . 4 . . . . . of the circuit is increased, the capacitor will take longer to be fully energised. |
1 / charge
2 / current 3 / potential difference 4 / resistance |
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LED
motor |
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G and J
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For P she could use . . . . .
For Q she could use . . . . . For R she could use . . . . . For S she could use.... |
P) An LDR (Light Dependent Resistor)
Q) A thermistor R) OR gate S) NOT gate |
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a) In this circuit the transistor acts as a __________________
b) As the amount of light decreases, the resistance of component M increases. What happens to the voltage across M and N? c) The purpose of the diode is to protect . . . . . |
a) Switch
b) Voltage across M increases. Voltage across N decrease. c) the transistor when the realy coil is swtiched on and off. |
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The circuit can be changed so that it gives a warning when a machine becomes too hot. Which of the statements is correct?
A M should be an LDR, and the output device could be an LDR B M should be an LDR, and the output device could be an LED C M should be a thermistor, and the output device could be an LDR D M should be a thermistor, and the output device could be an LED |
D
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What are some examples of input sensors
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Pressure switch
reed switch ariable resistor thermistor LDR (light dependent resistor) microphone |
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What are some examples of output devices?
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LED
bulb buzzer loudspeaker relay electric heater electric bell electric motor |
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Typically a minimum of two electric circuits are needed in a cathode ray tube. What are they for?
What could a third be used for? |
One circuit is used to heat the filament. Heating is necessary for thermionic emission to occur. Another circuit is needed for the cathode and anode so that an electric field is created between the two. (The cathode anode set up is to give the electron kinetic energy.
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a) What does eV stand for?
b) What is it a unit of? c) How is it defined? |
a) electron volt
b) energy c) The kinetic energy gained by an electron moving through a potential difference of one volt. |
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A tungsten filament is heated and particles are given energy by the placement of a cathode and andode.
a) What are the particles that are released? b) What is the purpose of the cathode and anode? |
a) electrons
b) Give the electrons kinetic energy, |
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a) What is the symbol for a thermistor?
b) What happens to the following when it is heated? resistance? current? |
b) Resistance is less
Current is higher |
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What is the symbol for a Light Dependent Resistor (LDR)?
What happens to the following when it is brighter? Resistance? Current? |
When it is brighter, the resistance is less.
When it is brighter, the current is higher. |
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In a cathode ray tube, how can you inrease the strength of the deflection?
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Increase the voltage across the y plates or x plates.
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What is the purpose of the fluorescent screen in the cathode ray tube?
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Show where the electrons are colliding/hitting/going. When the electrons hit the fluoresecent material, it glows.
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What type of gas do you want inside a cathode ray tube and why?
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None, you want a vacuum. If there is any gas, the electrons will collide with the gas particles and not form the beam of electrons.
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What is the name of the device used to change voltage across a component or device in a circuit?
What does the symbol look like? |
Potential divider or Potentiometer
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a) What is the purpose of this circuit?
b) Explain how it works |
a) Turn on the light when it is dark.
b) When it is dark, the resistance of the LDR increases. The voltage across the LDR increases. This increases the flow of base current which switches on the transistor. The current flow through the bulb into the collector and through the emitter of the transistor and the bulb lights up. |
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a) In this circuit, what condition must be true for the lightbult to light up?
b) What would happen if the 10kohm resistor and the LDR were switched? |
a) The LDR must be in the dark
b) The lightbulb would turn on when the LDR is in the light. |
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How would changing the size of the 10kohm resistor change the functioning of this circuit?
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This would change the intensity of light necessary to switch on/off the lightbulb.
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How does this circuit work?
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When the thermistor is cold it's resistance increases, and therefore the potential difference across it increases. This increases the base current into the transistor and allows the LED to turn on. When the circuit is warmer, the resistance of the transistor is lower, the potential difference across it lower, and there is not enough base current for the transistor to switch on. Therefore, the LED does not light.
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This circuit is designed so that the LED turns on when the thermistor is cold. How would it change if the resistor on the top left and the thermistor changed places?
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The LED would turn on when the thermistor is warm, or when the circuit is heated.
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What could you put in place of the LDR to make this a time delay switch?
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A capacitor. The transistor would switch on after a time delay.
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