C2:Electricity Flashcards

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1
Q

what is p.d

A

a measure of how much energy is transferred by each coulomb of electron

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2
Q

what is current

A

rate of flow of charge (how many coulombs pass every second)

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3
Q

how do you calculate p.d

A

energy transferred/charge flow

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4
Q

how do you calculate current

A

charge/time

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5
Q

what is resistance

A

a measure of how much a component resist the flow of charge

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6
Q

what is a resistor

A

heats up when current flows through it

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7
Q

how are current and pd similar

A

directly proportional

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8
Q

how do you calculate resistance
(ohms law)

A

p.d/current

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9
Q

why does a larger current mean an increase in resistance

A

more heat means more movement of ions which causes more collisions which cause a higher resistance

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10
Q

whats a diode

A

only lets a current flow in one direction

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11
Q

what are the rules for a series circuit

A

total p.d is shared between components
current is the same
resistance is added together

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12
Q

what are the rules for a parallel circuit

A

p.d of battery = p.d of components
current split between
total resistance is less than the resistance of the smallest resistor

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13
Q

what is a thermistor

A

as temperature increases resistance decreases

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14
Q

power =

A

p.d x current

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15
Q

what does the neutral wire do (blue)

A

takes the current back to the source and stays ay 0v

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16
Q

what does the live wire do (brown)

A

averages out the p.d to 230v
changes between positive and negative potentials

17
Q

what does the earth wire do (yellow and green)

A

safety wire which sends the current in the earth if the device becomes faulty

18
Q

what is a fuse

A

melts and reduces the current

19
Q

what do step up transformers do

A

increases voltage but decreases current to reduce the amount of power lost to heat

20
Q

what does a step down transformer do

A

reduces voltage down to a safer and useable 230v for homes

21
Q

why does resistance change for a metal

A

metals consists of a grid of ions surrounded by a sea of delocalised electron
They collide with ions and create heat
The higher the current the more frequent the collisions are which makes the ions vibrate more and makes it harder for electrons to flow
The resisitance has increased

22
Q

what happens to resistance in a diode

A

low resisitance in forward direction
high resistance in reverse direction

23
Q

whats the practical for resistance

A

metal wire with crocodile clips connected to it that has a circuit attached to it
move one clip along the wire
you should end up with a straight line through the origin
shows resistance and length of wire are directly proportional

24
Q

what is a ldr

A

light intensity increases and resistance decreases

25
Q

what does direct p.d cause (p.d that only flows in one direcion)

A

results in direct current in battery

26
Q

what types of fuses do we use

A

3a
5a
13a

27
Q

what is the national grid

A

network of power stations and net grids that transport electricity

28
Q
A