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GCSE Physics > 10) Electricity & Circuits > Flashcards

10) Electricity & Circuits Flashcards

1
Q

What is current?

A

Current is flow of electric charges, measured in amperes (A)

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2
Q

What is the value of current in a closed loop?

A

Current has the same value at any point in a closed loop

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3
Q

How is the flow of charge (C) calculated?

A

Flow of charge (C) = current (A) x time (s)

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4
Q

How is current calculated?

A 
current = charge / time
I = Q / t
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5
Q

What is the symbol for current?

A

I is the symbol for current

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6
Q

What is the symbol for charge?

A

Q is the symbol for charge

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7
Q

What is the symbol for time?

A

t is the symbol for time

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8
Q

What are electrical insulators?

A

Electrical insulators are a material that don’t allow electric currents to pass through them

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9
Q

What are examples of electrical insulators?

A

Plastic

Glass

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10
Q

What are electrical conductors?

A

Electrical conductors are a material which allow electric current to pass through them

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11
Q

What are examples of electrical conductors?

A

All metals

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12
Q

Why can’t electrical insulators conduct electricity?

A

Electrical insulators cannot conduct electricity as there are no freely moving electrons

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13
Q

What is potential difference?

A

aka. voltage, potential difference is the difference in the amount of energy that charge carriers have between two measured points in a circuit

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14
Q

What is potential difference measured in?

A

Volts

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15
Q

How is voltage calculated? (in relation to energy and charge)

A 
voltage = energy / charge
V = E / Q
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16
Q

What is the symbol for energy?

A

E is the symbol for energy

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17
Q

How is 1 volt calculated?

A

1 volt = 1 joule / coloumb

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18
Q

What do ammeters do?

A

Ammeters measure the flow of current passing through them, connected in series

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19
Q

What do voltmeters do?

A

Voltmeters measured the potential difference between two points in a circuit, connected in parallel

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20
Q

What is resistance?

A

Resistance is a measure of how difficult it is for current to flow through a component

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21
Q

How is resistance measured?

A

Ohms Ω

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22
Q

How is the size of current affected?

A

Higher resistance = decreased current

Higher potential difference = increased current

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23
Q

How is resistance calculated?

A 
Resistance = Voltage / Current
R = V / I
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24
Q

What is the symbol for voltage?

A

V is the symbol for voltage

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25
Q

How do wires affect resistance?

A

A longer, thinner wire has more resistance than a shorter, fatter wire

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26
Q

How is an ohmic conductor different to normal conductors?

A

The resistance through an Ohmic conductor remains constant as the current changes

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27
Q

What is Ohm’s law?

A 
resistance = potential difference / current
R = V / I
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28
Q

How is wire thickness calculated?

A

Cross sectional area = πr^2

Therefore doubling a wire’s thickness quadruples cross sectional area

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29
Q

What is resistance proptional to?

A

Resistance is proportional to the length (m) / cross sectional area (m^2)

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30
Q

What does a current-voltage graph look like for a resistor?

A

A straight line obeys Ohm’s law. Slope = 1 / resistance

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31
Q

What does a current-voltage graph look like for a filament lamp?

A

The gradient decreases at larger potential differences creating an S shape. This is due to increasing heat increasing resistance

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32
Q

How does charge flow?

A

Charge flows from the energy source through the circuit and its components

33
Q

How is energy transfer (J) calculated?

A

amount of energy transferred (J)= charged moved (coulombs) x potential difference (V)

34
Q

How is power calculated?

A

P = I x V

35
Q

How is power calculated with current and resistance?

A

P = I^2 x R

36
Q

How is power calculated with energy and time?

A

P = E / t

37
Q

What happens when a current flows through a resistor?

A

When a current flows through a resistor, electrons collide with particles transferring energy in the form of heat

38
Q

How is heat loss in a circuit reduced?

A

Using low resistance wires reduces heat loss in a circuit

39
Q

What are advantages of the heating effect in circuits?

A

Generates useful heat from electrical current (kettle)
Emits light in filament bulbs
Causes fuses to melt

40
Q

What are disadvantages of the heating effect in circuits?

A

Energy is lost in heating transmission wires

Some components work less efficiently when hot

41
Q

What is the circuit diagram symbol for a lamp?

A

A circle with a cross in the middle

42
Q

What is the circuit diagram symbol for a heater?

A

Four short rectangles stacked in a line

43
Q

What is the circuit diagram symbol for a magntesising coil?

A

A long, thin rectangle

44
Q

What is the circuit diagram symbol for an electric bell?

A

A semicircle with two straight lines originating from the flat side

45
Q

What is the circuit diagram symbol for a fixed resistor?

A

A rectangle

46
Q

What is the circuit diagram symbol for a variable resitor?

A

A rectangle with a diagonal arrow pointing to the top right corner

47
Q

What is the circuit diagram symbol for a galvanometer?

A

A circle with an arrow pointing up inside

48
Q

What is a galvanometer?

A

A very sensitive ammeter

49
Q

What is a diode?

A

A component which only allows current to flow through it in one direction

50
Q

What is a rectifier?

A

A component that turns an AC current into a DC

51
Q

How do diodes act as recitifers?

A

They dioide block the AC when it changes direction

52
Q

What are thermistors and LDRs?

A

Devices where resistance changes with temperature or light

53
Q

What is a thermistor?

A

A component thats resistance changes with its temperature

54
Q

What can a thermistor be used for?

A

Turning a heater off when a house reaches certain temperatures

55
Q

What are LDRs?

A

Devices where resistance changes with light intensity

56
Q

What does LDR stand for?

A

Light dependent resistor

57
Q

What can an LDR be used for?

A

Switching lights on when it gets too dark (phone camera flash)

58
Q

What effect will increased light intensity have on an LDR?

A

Decreased resistance

59
Q

What effect will increased temperature have on a thermistor?

A

Decreased resistance

60
Q

What is true of the current in a series circuit?

A

The current is the same at all points of the circuit

61
Q

What is true of the voltage in a series circuit?

A

The voltage across each component is different

62
Q

How is the total resistance calculated in a series circuit?

A

Adding up resistances of each individual resistor

63
Q

What do resistors do?

A

Oppose the flow of electric current

Increase resistance in a circuit

64
Q

How is a battery made?

A

Joining cells together

65
Q

How is the total potential difference calculated in a series circuit?

A

Adding all energy sources’ individual voltages

66
Q

In a series circuit what is the total voltage of energy sources equal to?

A

total voltage of energy sources = total potential difference across all components

67
Q

How are components connected in a series circuit?

A

In a row

68
Q

How are components connected in a parallel circuit?

A

On separate branches of wires to the energy source

69
Q

How is the current through an energy source in a parallel circuit calculated?

A

Adding the currents of each separate branch

70
Q

How does resistors in parallel affect the resistance?

A

Lower resistance

71
Q

What are the two advantages of parallel circuits?

A

Each branch can be switched on and off separately

If one branch breaks the current still flows through the others

72
Q

What is the equation for power?

A

power = potential difference x current

73
Q

What do power stations create?

A

An electric current which is an energy carrier

74
Q

What voltage electricity do power stations produce?

A

25,000 V

75
Q

What do step-up transformers do?

A

Increase the potential difference to 400,000 V

76
Q

What are the benefits of step-up transformers?

A

reduced current reduces heat loss across the country which increases the National Grid efficiency

77
Q

What do step-down transformers do?

A

Reduce the voltage to a lower value to make electricty safer (230 V)

78
Q

Why can live wires still be dangerous when turned off?

A

They may still hold some potential difference

GCSE Physics (14 decks)

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