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electricity Flashcards

(44 cards)

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1
Q

what is the function of a wire?

A

to carry electrical current

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2
Q

what is the function of a cell?

A

provide energy to a circuit

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3
Q

what is the function of a battery?

A

multiple cells found together in a circuit

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4
Q

what is the function of a closed switch?

A

the circuit is on

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5
Q

what is the function of an open switch?

A

the circuit is off

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6
Q

what is the function of a filament lamp?

A

turns electrical energy into light energy

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7
Q

what is the function of a fixed resistor?

A

to control the amount of current in a circuit

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8
Q

what is the function of a variable resistor?

A

the current is manually controlled

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9
Q

what is the function of a thermistor?

A

resistance changes as temperature changes

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10
Q

what is the function of a light dependent resistor?

A

resistance changes as the brightness changes

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11
Q

what is the function of a fuse?

A

safety devices designed to cut off a current if it gets too hot

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12
Q

what is the function of a diode?

A

one way valve, only allows current to flow in one direction

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13
Q

what is the function of a light emitting diode?

A

only allows current to flow in one direction and it emits light!

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14
Q

what is the function of an ammeter?

A

used to measure current in Amps(A), must be placed in series

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15
Q

what is the function of a voltmeter?

A

used to measure potential difference in volts (V), must be placed in parallel

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16
Q

what are delocalised electrons?

A

free electrons that are able to move in metals

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17
Q

what are sub atomic particles?

A

particles that are smaller than the atom e.g. protons, neutrons and electrons

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18
Q

what is the formula for charge?

Study These Flashcards
A

charge= current x time

19
Q

what is a coulomb?

Study These Flashcards
A

one coulomb is the amount of charge that passes in 1 second when the current is 1 ampere.

20
Q

what is current and its equation?

Study These Flashcards
A

current is the rate of the flow of charge
current= charge / time

21
Q

what happens to the current in a series circuit?

Study These Flashcards
A

in series circuits, the current stays the same at all points in the circuit

22
Q

what happens to the current when more lamps are added?

Study These Flashcards
A

adding more lamps increases the resistance which reduces the current

23
Q

what happens to the potential difference in a series circuit?

Study These Flashcards
A

the potential difference is shared between the components

24
Q

what happens to the potential difference and current in parallel circuits?

Study These Flashcards
A

in parallel circuits, the current splits between the different branches but the p.d. is the same for every branch

25
what is the formula for potential difference?
potential difference= current x resistance
26
how do you find the total resistance in a series circuit?
add all of the resistors together
27
what is the relationship between length of wire and resistance?
as the length of the wire increases, the resistance increases
28
describe and explain the I/V curve for a fixed resistor
as p.d. increases, current increases. the relationship is directly proportional a fixed resistor is an ohmic conductor meaning it follows ohm's law
29
describe and explain the I/V curve for a filament lamp
as the p.d. increases so does the current but after a certain point the current levels out for small values of p.d. a filament lamp is an ohmic conductor, as the bulb gets hotter, resistance increases which limits the maximum current
30
describe and explain the I/V curve for a diode
negative values of p.d. result in zero current, positive values of p.d. will eventually result in current flowing a diode is a device that only allows current to flow in one direction, for negative values there is zero current flowing , for positive values, current will eventually flow, when the breakdown voltage is reached
31
what is direct current?
where the potential difference does not change so the current travels in one direction e.g. cells
32
what is alternating current?
if the potential difference repeatedly changes direction then the current would repeatedly change too e.g. mains electricity
33
describe the mains supply in the UK
the mains supply in the UK as a potential difference of 230V and a frequency of 50Hz
34
what are the three different wires in UK 3-pin plug?
- earth wire (blue and green) - neutral wire (blue) - live wire (brown)
35
describe the earth wire
the earth wire is plugged in first and out last, it is the safety wire as if a fault develops, the live wire touches the metal case and the current flows to the ground- it is connected to the ground, sends extra voltage to the earth stake so it is a 0V
36
describe the neutral wire
takes the voltage out , as an insulated base and completes the circuit, it is also at 0V as it takes the voltage out
37
describe the live wire
carries alternating current and also has an insulated base, carries voltage at 230V so it is a very dangerous wire
38
describe the safety features of a UK plug
the cable grip helps to keep the wire secure, fuse breaks the circuit if the current gets too high, the earth wire is plugged in first and comes out last, plastic insulation/cover
39
what is the national grid?
the national grid is the network of cables and transformers which transmits electricity across the country, it is made up of transformer and pylons
40
what is the electrical power equation?
power= potential difference x current
41
what do the transformers do in the national grid?
transformer change the potential difference and current of the electricity transmitted by the national grid - step up transformer: p.d. goes up, current goes down -step down transformer: p.d. goes down, current goes up
42
why does the potential difference and the current need to be changed?
low currents help stop the cables from heating up and so reduce thermal energy transfer from the transmission cables to the surroundings, a very high potential difference means that a lower current is needed to transmit the same amount of power
43
what is the pet equation?
power= energy / time
44
what is the waste power equation?
power= (current)² x resistance

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