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physics paper 1 > electricity > Flashcards

electricity Flashcards

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1
Q

what is electric current

A

it is the flow of electrons from the NEGATIVE tot he POSITIVE end of a cell

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2
Q

what is current

A

it is the flow of electrical charge around a circuit and is measures in amperes and can be measures using ammeters

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3
Q

what is the conventional current

A

it is the idea that electrons flow from the positive end of a cell to the n negative end

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4
Q

how is current distributed in a series circuit

A

current can never be used up meaning that it will be the same around the whole circuit

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5
Q

how is current distributed in a parallel circuit

A

the total current of each branch is equal to the total current flowing

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6
Q

what is potential difference

A

one volt is one joule of energy is transferred for each coulomb of charge
it is the difference in the amount of energy between two points in a circuit

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7
Q

what happens to potential difference in a series circuit

A

the total potential difference in the circuit is equal to the potential difference of the cell

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8
Q

what happens to the potential difference in a parallel circuit

A

the voltage across each branch is te same as the cells

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9
Q

what is the charge flow in a circuit

A

it is measured in coulombs and one ampere is one coulomb flowing per seconds. the size of the current is the rate of flow of electrical charge

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10
Q

what is the formula for charge flow

A

it is charge flow (coulombs) = current (A) * time (seconds)

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11
Q

what is the formula for energy transferred

A

energy transferred (J) = charge flow C (coulombs) * potential difference (V)

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12
Q

what is the formula for energy transferred

A

energy transferred (J) = charge flow (C coulombs) * potential difference (V)

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13
Q

what is resistance

A

it is the potential difference required to drive a current through an electrical component
or how easily an object resists current

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14
Q

what is the formula for voltage

A

V = I * R or voltage = current * resistance

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15
Q

what does a current -voltage graph look like for an ohmic component

A

a directly proportional graph with a straight line

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16
Q

what is an ohmic component

A

a component that does not change its resistance as you increase the current. However the resistance will only stay constant at a constant temperature

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17
Q

what does the current voltage graph look like for a non ohmic component

A

it is not directly proportional and gets flatter as the component gets hotter

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17
Q

what does the current voltage graph look like for a non ohmic component

A

it is not directly proportional and gets flatter as the component gets hotter

18
Q

why does the resistance increase at high temperatures

A

at high temperatures the atoms vibrate more causing the electrons in the current to collide more meaning more energy is needed to push the current

19
Q

what is a diode

A

a compontent that has very little resistance in the forwards direction but high resistance in the backwards direction

20
Q

what happens to the resistance in a series circuit

A

the total resistance is the resistance of all components and resistors added together

21
Q

what happens to the resistance in a parallel circuit

A

the total resistance is smaller than the smallest resistor

22
Q

what does a current to voltage graph look like for a resistor

A

it is directly proportional

23
Q

what happens to the resistance of an LDR when light changes

A

as light increases the resistance decreases and as the light levels decrease the resistance increases

24
Q

what happens to the resistance of the thermistor as the temperature changes

A

at low temperatures it has a very high resistance and at high temperatures it has low resistance

25
Q

how to measure resistance against the length of a wire

A

use a circuit that measures voltage and current and the use crocodile clips on a piece of wire attached to a ruler to adjust the length

26
Q

what is the relation of resistance to the length of the wire

A

they are directly proportional

27
Q

what is zero error and how can it be accounted for

A

zero error is a reading on a measuring instrument when the value should be zero and this is a systematic error which cannot be solved by doing repeats. In order to account for this we need to subtract this value from all of our readings.

28
Q

how can we improve the test to see the affect of altering resistance on a circuit

A

use a variable resistor or a piece of coiled wire that has a slider that changes its resistance

29
Q

what is the power rating of an appliance

A

it is the amount of energy transferred every second

30
Q

what usually has a higher power rating thermal energy appliances of kinetic

A

thermal energy

31
Q

what is the formula for energy

A

energy (J) = power (W) * time (s)

32
Q

what is the formula for power

A

Power (W) = current (A) * voltage (V)

33
Q

what is the formula for power

A

Power (W) = current squared (A) * resistance

34
Q

what is DC voltage

A

it is the current from a cell that only moves in one direction

35
Q

what is AC voltage

A

it is when the current is constantly changing direction

36
Q

what is the benefit of alternating current

A

it is very easy to use a transformer to increase or decrease the potential difference

37
Q

what is the frequency of the main UK electricity

A

it is 50 hertz or switches direction to complete one cycle 50 times a second

38
Q

how many volts is the mains UK electricity

A

around 230 V

39
Q

what is the function of the live wire

A

the live wire is the brown wire and carries the alternating potential difference from the supply (230V). The live wire is connected to a fuse in the plug

40
Q

what is the function of the neutral wire

A

the neutral wire is the blue one and completes the circuit

41
Q

what is the function of the earth wire

A

the green and yellow striped earth wire acts a safety wire to stop the appliance becoming live. If the appliances metal case becomes live electricity flows into the earth wire which is connected to the ground which offsets a huge current to the earth melting the fuse

42
Q

what is the national grid

A

it contains high voltage cables and transformers and transfers energy across the UK

43
Q

what do step up transformers do

A

they increase the voltage to several thousand volts as less energy is lost when it has a high voltage

physics paper 1 (5 decks)

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