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Physics > Unit 10 & 11 - Electricity And Circuits/ Static Electricity > Flashcards

Unit 10 & 11 - Electricity And Circuits/ Static Electricity Flashcards

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1
Q

What are ‘free electrons’?

A

When the electrons in a metal in the outer shell can easily be removed due to a weak force

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2
Q

What does a voltage do?

A

It pushes the free electrons around the circuit

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3
Q

What is the direction of a conventional current?

A

From positive terminal to negative terminal of a battery

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4
Q

What is electric current measured in?

A

Amperes (amps)

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5
Q

What is current?

A

The flow of electrons in a circuit (like speed)

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6
Q

What does ‘current being conserved’ mean?

A

The current leaving the positive terminal is equal to the current arriving at the negative terminal.

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7
Q

What happens to the current in a parallel circuit?

A

It splits at its branches

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8
Q

What is another name fore voltage?

A

Potential difference

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9
Q

What 2 things must there be for a current to flow?

A

The circuit must be closed and there must be a potential difference

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10
Q

How does a bigger p.d affect the current

A

It is bigger

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11
Q

What is the p.d rule for a parallel circuit?

A

The total is split evenly across the branches

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12
Q

What is the potential difference measured in?

A

Volts

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13
Q

How is a voltmeter placed in a circuit?

A

In parallel around a component

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14
Q

What forms an electric current?

A

Moving charged particles

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15
Q

What is electric charge measured in?

A

Coulombs (C)

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16
Q

What is a charge?

A

The charge that passes the point in a circuit per second

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17
Q

What is electric current?

A

The rate of flow of charge

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18
Q

What is the equation for charge

A

Charge = current x time

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19
Q

What is the symbol for current?

A

I

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20
Q

What is the symbol for charge?

A

Q

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21
Q

what is electric potential energy?

A

The energy transferred to the charge from the cell, when something has the ‘potential’ to transfer energy

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22
Q

How is energy transferred in a circuit?

A

A cell stores chemical energy
Energy is transferred to the charge
That charge transferred energy to components, it has potential energy
Energy transfers to the lamp is transferred to the surrounding by heating and by light.

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23
Q

In terms of energy, what does the potential difference show

A

The amount of potential energy the cell transfers to each coulomb of charge

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24
Q

What is the equation for energy transfers

A

Energy transferred - charge moved x p.d

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25
Q

What is the symbol for p.d

A

V

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26
Q

What is resistance measured in?

A

Ohms

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27
Q

What is the equation relating p.d, current and resistance

A

V = I x R

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28
Q

What happens when a resistor is added in a series circuit

A

The resistance increases

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29
Q

What happens to the resistance when another resistor is added in parallel

A

The resistance decreases as there are more pathways

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30
Q

What is a variable resistor

A

A resistor where the resistance can be changed

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31
Q

What does direct proportion mean?

A

When one factor increases, the other does by the same %

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32
Q

What does it show if the p.d increases but the current doesn’t

A

The resistance is increasing

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33
Q

What is a diode

A

A component used in a circuit to keep the current flowing in one direction

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34
Q

What does LDR stand for?

A

Light-dependent resistor

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35
Q

When does a LDR have a high resistance?

A

In the dark

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36
Q

What are thermistors

A

Components that have high resistance at low temperatures

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37
Q

Explain the core practical - Investigating resistance

A

Set up a simple circuit with resistor around voltmeter and ammeter
Set power pack on lowest voltage and note p.d.
Increase voltage
Repeat with lamps and parallel circuits

38
Q

Why is energy transferred when a current passes through a resistor and how?

A

Electrical work is done against the resistance, energy is transferred by heating

39
Q

What does dissipated mean?

A

Spread out

40
Q

Why is it bad for heat to be transferred by heating in a computer

A

Useful energy is being transferred and wasted

41
Q

What does the inside of a resistor contain?

A

Free electrons and a lattice of positive ions

42
Q

How does a resistor work?

A

Electrons flow through the lattice and collide with the ions

There is a higher resistance if there are more ions (more collisions) and more energy is transferred

43
Q

What are the 3 ways resistance can be decreased

A

Low resistance metals for wires
Thicker wires
Cooling metals (lattice isn’t vibrating as much)

44
Q

Why might you want to lower the resistance?

A

So not as much energy is transferred to the surroundings

45
Q

What is the equation for energy transferred

A

E = I x V x t

46
Q

What does the energy transferred by an electric current depend on

A

The time taken

47
Q

What is power

A

The energy transferred per second

48
Q

What is the equation for power (energy transfer)

A

P = E/t

49
Q

What is the equation for power? (Current)

A

P = I x V

50
Q

What is power directly proportions to?

A

The p.d

51
Q

What is the equation for power (resistance)

A

P = I^2 x R

52
Q

What are the mains electricity

A

A source of energy that appliances use if they need a late amount of energy

53
Q

What is the national grid

A

A network of cables and wires that transfer energy by electricity.

54
Q

What is direct current

A

When the direction of movement of charge stays the same

55
Q

What is alternating current

A

When the direction of the current changes

56
Q

Why is there alternating current in the mains

A

It is produced using generators that rotate

57
Q

What happens to the voltage in alternating current

A

It increases to a peak, decreases to zero and increases to a peak in the opposite direction

58
Q

In the UK, how many of the alternating current cycles are there per second?

A

50

59
Q

What is the frequency of the mains supply?

A

50Hz

60
Q

What is the voltage of the mains in the UK

A

230V

61
Q

What are the 4 components in a UK plug?

A

Earth (green and yellow)
Neutral (blue)
Live (red)
Fuse

62
Q

What is the role of the earth wire?

A

Connects metal parts to a large metal tubing in the ground which is at 0V for safety

63
Q

What is the role of the neutral wire

A

The return path to the power station, 0V

64
Q

What is the role of the live wire?

A

Connects appliances to generators at power station, 230V

65
Q

What is the role of the fuse?

A

A safety device that can only carry a certain amount of current, 3A, 5A or 13A

66
Q

What wire are switches connected to (plug)

A

Live wire

67
Q

How does a fuse work

A

It contains a thin wire, is the current is too high, the wire melts and the circuit is broken

68
Q

Why are metal parts of appliances connected to the earth wire?

A

Current from the metal parts of the appliance go into the ground instead of you

69
Q

Give to examples of the fuse blowing

A

Too high of a current used

The live wire touches a metal part (a lot of current passes)

70
Q

What are circuit breakers?

A

Devices that detect change in the current and can switch off the supply

71
Q

Give 2 advantages of a circuit breaker

A

Once a fault is fixed, they can be switched on again and not replaced
They work very quickly (don’t take as long)

72
Q

Why can plastics collect charge?

A

They are insulators

73
Q

What happens to electrons when you rub an acetate rod onto a duster

A

They move from the acetate to the duster, duster becomes negatively charged and rod positively charged

74
Q

What is static electricity?

A

When the charge is not able to flow away to the surroundings, in hair, they begin to repel eachother

75
Q

What is charging by induction?

A

When something’s charge changes but no charges have been transferred

76
Q

Explain how a charged balloon can induce a charge in a wall

A

The wall contains positive and negative charge. The negative charge is repelled by the negative charge on the balloon so the surface becomes positively charged. The positive charge has been induced

77
Q

Why might you feel a small electric shock?

A

If you pick up a charge from a carpet and touch a conductor, the electrons will flow in t(e gap

78
Q

What does earthed or discharged mean?

A

When a charge is removed from something

79
Q

How does static electricity build up in the clouds? (Thunder and lightning)

A

Friction between particles of ice and water moved by air currents, when the charge is large enough, the particles travel between the cloud and earth

80
Q

How are buildings earthed?

A

They have lighting conductors side of thick metal running down from their tops to the earth

81
Q

Why are sparks dangerous

A

When there is fuel vapour, it could ignite

82
Q

What is the danger for refuelling an aircraft

A

The fuel vapour becomes charged when flying through the air so can ignite

83
Q

What prevents a spark in an aircraft?

A

A bonding line is connected to the earth the aircraft before refuelling.

84
Q

How are cars earthed?

A

Though their tyres, which contain a form of carbon that makes them conducting

85
Q

What is electrostatic spraying?

A

When the nozzle of a spray contains a charge and charges the droplets as they pass, the charged droplets spread out due to repelling and are attracted to the plants by induction

86
Q

What is a force field?

A

A volume of space around an object where another object is affected by its force

87
Q

What metals are of magnetic material?

A

Steel, iron, nickel and cobalt

88
Q

What is an electric or electrostatic field?

A

The force field of a charged object

89
Q

What is a point charge?

A

Electric fields around a single point

90
Q

What are the 4 rules for field lines?

A

They never cross
Closer together = stronger force
Show direction of charge
Start at positive charge, end at negative charge

91
Q

What is a rule for an electric field between 2 parallel plates?

A

It is uniform

Physics (12 decks)

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