Electricity Flashcards

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1
Q

For the diagram of the atom name the parts.

A

See diagram

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2
Q

Which particles are in the nucleus of the atom?

A

Protons and neutrons

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3
Q

What happens if two positive charges are brought together?

A

They repel each other

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4
Q

What happens if two negative charges are brought together?

A

They repel each other

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5
Q

What happens if a positive and a negative charge are brought together?

A

They attract each other

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6
Q

What is electric charge?

A

An electric charge occurs when there are fewer or more electrons than protons.

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7
Q

Name one place that electrostatics can be used.

A
  • Laser printers
  • Paints spraying
  • Cling film
  • Forensic science
  • Dust removal
  • Electrostatic precipitators
  • Electrostatic separators
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8
Q

Explain how electrostatics can be used in paint spraying a car.

A
  • Car is connected to a negative terminal so that it is negatively charged.
  • Spray gun is made positively charged so the paint particles are positive.
  • The poistive paint is attracted to the negative car.
  • Areas of the car already covered in paint will repel any more charged paint.
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9
Q

What is the effect of an electric field on a charge?

A

The charge will experience a force.

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10
Q

What does an electric field line show?

A

The direction a positive charge would move in that field.

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11
Q

What would the field lines around a positive point charge look like?

A

Field lines show direction away from the positive point charge.

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12
Q

What would the field lines around a negative point charge look like?

A

Field lines show direction towards the negative point charge

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13
Q

What would the field lines look between parallel plates?

A

Field lines run from positive to negative plate, with a bulge at the ends of the parallel plate.

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14
Q

How can you indicate a stronger electric field?

A

More field lines

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15
Q

How can you indicate a weaker electric field?

A

Fewer field lines

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16
Q

How is a uniform electric field represented?

A

Evenly spaced field lines

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17
Q

What would happen to an electron being fired through the electric field below?

A

It would experience a force and be attracted to the positive plate

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18
Q

What is current?

A

The charge transferred per second

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19
Q

What is d.c.?

A

Direct current. Charges move in one direction only.

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20
Q

What is a.c.?

A

Alternating current. The charges change direction constantly

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21
Q

Name one source of d.c.

A

A battery

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22
Q

Name one source of a.c.

A

Mains supply

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23
Q

What type of current is represented by this oscilloscope image?

A

d.c.

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24
Q

What type of current is represented by this oscilloscope image?

A

a.c.

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25
Q

How can you tell from this oscilloscope image that this is a.c.?

A

The trace shows a change in direction

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26
Q

What is meant by the potential difference (voltage) of a supply?

A

It is the number of Joules of energy given to each coulomb of charge passing through the cell

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27
Q

Which device measures current?

A

Ammeter

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28
Q

Which device measures voltage?

A

Voltmeter

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29
Q

Which devi measures resistance?

A

Ohmmeter

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30
Q

What is the symbol for an ammeter?

A

A circle with an A in it

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31
Q

What is the symbol for a voltmeter?

A

A circle with a V in it

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32
Q

What is the symbol for an Ohmmeter?

A

Circle with an Omega in it

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33
Q

How should an ammeter be connected to measure the current in a component?

A

In series

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34
Q

How should a voltmeter be connected to measure the voltage across a component?

A

In parellel

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35
Q

How can you identify a series circuit?

A

It is a circuit with only one path round it

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36
Q

What is the rule for current in a series circuit?

A

The current is the same everywhere

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37
Q

What is the rule for voltages in a series circuit?

A

The voltage across each component added together is equal to the supply voltage.

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38
Q

What happens if you unscrew one of the lamps in the circuit below? Why?

A

The other lamps go out. There is a break in the circuit and the current does not have a complete route to the battery.

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39
Q

If you heat a conductor, what happens to it’s resistance?

A

It increases

40
Q

How can a parallel circuit be identified?

A

It is a circuit with more than one path round it.

41
Q

What is the rule for current in a parallel circuit?

A

The supply current is equal to the current in each branch added together.

42
Q

What is the rule for volatges in a parallel circuit?

A

The voltage across each branch is equal to the supply voltage.

43
Q

Which circuit component is represented by the following diagram?

A

Cell

44
Q

Which circuit component is represented by the following diagram?

A

Battery

45
Q

Which circuit component is represented by the following diagram?

A

Switch

46
Q

Which circuit component is represented by the following diagram?

A

Lamp

47
Q

Which circuit component is represented by the following diagram?

A

Motor

48
Q

Which circuit component is represented by the following diagram?

A

Loudspeaker

49
Q

Which circuit component is represented by the following diagram?

A

Resistor

50
Q

Which circuit component is represented by the following diagram?

A

Variable resistor

51
Q

Which circuit component is represented by the following diagram?

A

Thermistor

52
Q

Which circuit component is represented by the following diagram?

A

Light dependent resistor

53
Q

Which circuit component is represented by the following diagram?

A

Fuse

54
Q

Which circuit component is represented by the following diagram?

A

Capacitor

55
Q

Which circuit component is represented by the following diagram?

A

Diode

56
Q

Which circuit component is represented by the following diagram?

A

Light emitting diode

57
Q

Which circuit component is represented by the following diagram?

A

Photovoltaic cell/solar cell

58
Q

Which circuit component is represented by the following diagram?

A

Microphone

59
Q

Which circuit component is represented by the following diagram?

A

Transistor

60
Q

Which circuit component is represented by the following diagram?

A

MOSFET

61
Q

What is the function of a MOSFET?

A

Electronic switch

62
Q

What is the function of a transistor?

A

Electronic switch

63
Q

What is the energy change in a battery?

A

Chemical to electrical

64
Q

What is the energy change in a bulb?

A

Electrical to light (+heat)

65
Q

What is the energy change in a motor?

A

Electrical to kinetic

66
Q

What is the energy change in a loudspeaker?

A

Electrical to sound

67
Q

What is the energy change in a buzzer?

A

Electrical to sound

68
Q

What is the energy change in a LED?

A

Electrical to light

69
Q

What is the energy change in a photovoltaic cell?

A

Light to electrical

70
Q

What is the energy change in a microphone?

A

Sound to electrical

71
Q

What happens if you increase the resistance in a circuit?

A

The current will decrease

72
Q

State two places a variable resistor can be used.

A
  • Light dimmer switch
  • Speed control on Scalextric cars
  • Volume control on a radio
73
Q

State a device that can be used in a temperature sensor

A

Thermistor

74
Q

State a device that can be used in a light sensor

A

LDR

75
Q

What is a thermistor?

A

A resistor whose resistance changes with changes in temperature

76
Q

What is a Light Dependent Resistor?

A

A resistor whose resistance changes with changes in light level

77
Q

What is a fuse?

A

A safety device that protects the circuit from surges in current

78
Q

Explain how a fuse works.

A

A fuse is a thin wire. If too much current passes through it, it will get hot and melt. This breaks the circuit.

79
Q

How should a diode or LED be connected with a battery to light correctly?

A

Small line on battery points to small line on LED or diode.

80
Q

Why is an LED normally connected in series with a resistor?

A

Resistor is to protect the LED by limiting the current in the LED.

81
Q

What does a capacitor do?

A

Stores charge or energy

82
Q

What will be the voltage across a capacitor when it is fully charged?

A

The supply voltage

83
Q

What will be the voltage across a capacitor when it is fully discharged?

A

Zero volts

84
Q

What is meant by capacitance?

A

Charge stored per unit volt

85
Q

What is the rule for selecting a fuse from a power rating?

A

Appliances less than 720W use a 3A fuse Appliances more than 720W use a 13A fuse

86
Q

What is power?

A

The energy used per second

87
Q

What two factors effect the running cost of an appliance?

A
  • The time it is used for
  • The power rating of the appliance
88
Q

How can power losses be reduced in transmission lines?

A

By increasing the transmission voltage and so decreasing the transmission current.

Power loss P = I2R, so if the current is reduced the power lost is reduced.

89
Q

What is the charge on a proton?

A

Positive

90
Q

What is the charge on a neutron?

A

No charge

91
Q

What is the charge on an electron?

A

Negative

92
Q

What is the stated value of the mains?

A

230V, 50Hz

93
Q

When would you use a relay?

A

To switch on a high current circuit using a low current circuit for safety.

94
Q

How does a relay work?

A
  • Close a switch to make a current flow in a wire.
  • This creates an electromagnet.
  • Electromagnet attracts metal switch.
  • This completes the second circuit and the lamp switches on.
95
Q

Which component does the symbol represent?

A

Buzzer

96
Q

What is the energy change in a buzzer?

A

Electrical to sound