electricity Flashcards

1
Q

What is the symbol for an open switch?

A
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2
Q

What is the circuit symbol for a closed switch?

A
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3
Q

What is the circuit symbol for a cell?

A

Cell

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4
Q

What is the circuit symbol for a battery?

A

Battery

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5
Q

What is the circuit symbol for a diode?

A

Diode

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6
Q

What is the circuit symbol for a resistor?

A

Resistor

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7
Q

What is the circuit symbol for a variable resistor?

A

Variable resistor

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8
Q

What is the circuit symbol for an LED (light emitting diode)?

A

LED

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9
Q

What is the circuit symbol for a lamp?

A

Lamp

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10
Q

What is the circuit symbol for a fuse?

A

Fuse

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11
Q

What is the circuit symbol for a voltmeter?

A

Voltmeter

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12
Q

What is the circuit symbol for an ammeter?

A

Ammeter

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13
Q

What is the circuit symbol for a thermistor?

A

Thermistor

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14
Q

What is the circuit symbol for an LDR (light dependent resistor)?

A

LDR

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15
Q

What does a cell/battery do?

A

Pushes electrons around a complete circuit

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16
Q

What does a switch do?

A

Enables the current in a circuit to be switched on or off

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17
Q

What does a diode do?

A

Allows current through in one direction only

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18
Q

What does an LED (light-emitting diode) do?

A

Emits light when a current passes through it

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19
Q

What does an ammeter do?

A

Measures electric current

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20
Q

What does a voltmeter do?

A

Measures potential difference in a circuit

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21
Q

What does a (fixed) resistor do?

A

Limits the current in a circuit

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22
Q

What does a variable resistor do?

A

Allows the current to be varied

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23
Q

What does a fuse do?

A

Melts and breaks the circuit if the current through it is greater than a certain amount

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24
Q

What does a thermistor do?

A

A type of resistor that decreases its resistance if its temperature increases (and vice versa)

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25
What does an LDR (light-dependent resistor) do?
Reduces its resistance if the light intensity increases
26
How should an ammeter be connected if it is measuring the current through a bulb?
In series with the bulb
27
How should a voltmeter be connected if measuring the voltage across a bulb?
In parallel with the bulb
28
What is potential difference?
Energy transferred to a bulb by each coulomb of charge that passes through it
29
What is electrical resistance?
How difficult it is for electrons to pass through a component in a circuit
30
What is Ohm's law?
The current through a resistor at constant temperature is directly proportional to the potential difference across the resistor
31
What is an ohmic conductor?
A conductor that obeys Ohm's law - its voltage is directly proportional to its resistance at a constant temperature
32
How is current distributed in a series circuit?
It is the same for every component in the circuit
33
How is voltage distributed in a series circuit?
It is shared between the components
34
What is resistance like in a series circuit?
The total resistance is equal to the sum of the resistance of each component
35
What does adding more resistors in a series circuit do to the total resistance?
It increases
36
How is current distributed in a parallel circuit?
It is shared: the total current is the sum of the currents through the separate branches
37
How is potential difference distributed in a parallel circuit?
The potential difference across each component is the same
38
What is resistance like in a parallel circuit?
The total resistance of all the components is less than the resistance of the resistor with the least resistance
39
What does adding more resistors in a parallel circuit do to the total resistance?
It decreases
40
What is direct current?
Current that flows in one direction only
41
What is alternating current?
Current that repeatedly changes direction
42
What type of current is used for mains electricity in the UK?
Alternating current
43
What is the mains frequency in the UK?
50 Hz
44
What is the national grid?
A nationwide network of cables and transformers
45
What is the voltage of the domestic electricity supply?
230V
46
What is the sequence of the national grid?
Power stations --> step-up transformer --> transmission cables --> step-down transformers --> consumers
47
What does a step-up transformer do?
They increase the voltage of the electricity, meaning less current is needed to transfer the same amount of power. This reduces the power lost due to resistance heating the cables, making the national grid more efficient
48
What does a step-down transformer do?
Reduces the voltage to a safe level (230V) for consumers like homes or businesses
49
What colour is the earth wire in a plug?
Green and yellow
50
What colour is the live wire in a plug?
Brown
51
What colour is the neutral wire in a plug?
Blue
52
What does the earth wire do?
Connects the appliance to the earth so that, in the event of a fault, the appliance does not become live and current flows to the ground instead of through a person
53
What does the live wire do?
Carries the alternating voltage from the power supply
54
What does the neutral wire do?
Completes the circuit by carrying electricity back to the power source
55
What is (usually) the potential difference of the earth wire?
0V
56
Do appliances with plastic casings need an earth wire? Why?
No, because plastic is a good insulator and so if there was a fault, electricity would not flow from the appliance to a person
57
Which pin in a plug is the longest? Why?
The one connected to the earth wire so when an appliance is plugged in, it's automatically earthed
58
What are the pins in a plug made of? Why?
Brass because it is a good conductor, and it doesn't rust/oxidise
59
Where in the plug is the fuse located? Why?
Between the live pin and live wire so that if too much current passes through it, it melts and cuts the live wire off
60
What material is used in wires? Why?
Copper, as it is a good electrical conductor and bends easily
61
What is a short circuit?
When the live wire touches the neutral wire and a big current passes between the two wires at the point of contact. The fuse would then blow, cutting the current off
62
What happens if a person touched a live wire?
Because people's bodies are at 0 volts, a large voltage would act across their body and a current would flow through them. This would cause an electric shock
63
What is the power of an appliance?
The energy it transfers per second
64
What happens when insulating materials are rubbed against each other?
Electrons are rubbed off one material and onto another. The material that gains the electrons becomes negatively charged and the other material is left with an equal positive charge
65
What happens when two electrically charged objects are brought close together?
They exert a force on each other: two objects with the same charge repel, two objects with opposite charge attract