Topic Menu

P2.4.2 - AQA GCSE Physics Unit 2

P2.4.2

Current, charge and power

a) When an electrical charge flows through a resistor, the resistor gets hot.

Candidates should understand that a lot of energy is wasted in filament bulbs by heating. Less energy is wasted in power saving lamps such as Compact Fluorescent Lamps (CFLs) or LED lamps.

Candidates should understand that there is a choice when buying new appliances in how efficiently they transfer energy.

b) The rate at which energy is transferred by an appliance is called the power.

P = E/t

P is power in watts, W

E is energy in joules, J

t is time in seconds, s

c) Power, potential difference and current are related by the equation:

P = I x V

Candidates should be able to calculate the current through an appliance from its power and the potential difference of the supply, and from this determine the size of fuse needed.

P is power in watts, W

I is current in amperes (amps), A

V is potential difference in volts, V

d) Energy transferred, potential difference and charge are related by the equation:

E = Q x V

HT only