Physics - 5 Electricity in the Home - 5.3 Electrical Power and Potential Difference & 5.4 Electrical Currents and Energy Transfer & 5.5 Appliances and Efficiency

Energy transferred (in an electrical circuit) =

power x time

What forces electrons round a circuit?

work done by the power supply

The current through an electrical appliance is:

the charge that flows through it each second

The potential difference across an electrical appliance is:

the energy transferred to the appliance by each coulomb of charge that passes through it

The power supplied to an electrical appliance is:

the energy transferred to it each second

Power supplied =

current x potential difference

How should you choose a fuse?

choose one that is over the normal operating potential difference of the appliance

power = current² x resis

current² x resistance

The power supplied to a resistor is proportional to...

the square of the current

Charge flow =

current x time

Why does a resistor get hotter? [5]

- electrons are pushed round the circuit
- they bump into metal ions in the resistor
- this causes the ions to gain kinetic energy
- they vibrate
- the resistor gets hotter

A resistor becomes hotter when:

charge flows through the resistor, transferring energy to it

Coulomb

unit of charge

The energy supplied to an appliance depends on... [2]

- how long it has been switched on
- the power supplied to it

Efficiency values can be expressed as [2]:

- ratio
- percentage

Why do electrical appliances waste energy? [2]

- the heating effect of current in wires and components
- friction causes heating in appliances with moving parts