Physics GCSE 4 aqa

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Physics ­ Electricity
Charge is the amount of electricity
It is measured in coulombs (C )
Symbol is Q
Current is charge per second
the flow of electric charge around the circuit
only flows if there is a potential difference
It is measured in Amps (A) ­ measured with an ammeter ­ must be placed in series to measure the current
Its symbol of current is I
Resistance in a circuit will slow it down
Potential difference/Voltage
Voltage is the amount of energy per unit charge
Is the driving force that drives the current around the circuit
It is measured in Volts (V)
Measured with a voltmeter ­ must be placed in parallel around the component that you are testing
Resistance opposes the flow of current
Is measured in Ohms ( )
Charge is waiting in the circuit doing nothing ­ the potential difference does the work of pushing it ­ once it is
moving, the moving charge is called current
Current (A) = Charge (C) / time (seconds) (I = Q/t)
Potential difference (V) = Work done (J)/ Charge (C ) (V = WD / Q)
The potential difference/ Voltage across an electrical component is the amount of energy transferred by the
electrical component
The potential difference is the work being done per unit of charge
Circuit symbols

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Potential difference current graphs
It is the plot of current against voltage (I on the y axis and V on the x axis)
1. For different resisters ­ At a constant temperature the current is directly proportional to the voltage, as current
increases then so will voltage. Different resistors will have different slopes.
2. Filament Lamp ­ As the temperature of the lamp increase then so does resistance ­ so you get an s ­curve. As it
gets hotter, current increases more slowly
3.…read more

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Current is the same anywhere in the circuit ­ determined by the amount of supply and the amount of
3. Resistance adds up ­ R = R1 + R2... #
4. Cell (power supply) voltages add up i.e. one battery of 12v = 12v but two batteries of 12v =24v
Parallel Circuits
1. Parallel circuits give independence and isolation ­ you can disconnect one part of the circuit and all the other
parts will still work ­ e.g.…read more

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Inside the plug there should be no copper showing because it could touch the inside of the plug and burn it
The cable grip should be firm ­ to prevent pulling on the wires
Different appliances need different amount of current ­ the thicker the cable to less resistance and the more
Metal parts are copper and brass and the insulating parts are plastic and rubber (to be flexible an insulate)
Fuses (circuit breaker) and Earthing
If a fault develops where the live…read more

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