(c) Energy and voltage in circuits

Explain why a series or parallel circuit is more appropriate for particular applications, including domestic lighting

Understand how the current in a series circuit depends on the applied voltage and the number and nature of other components

Describe how current varies with voltage in wires, resistors, metal filament lamps and diodes, and how to investigate this experimentally

Describe the qualitative effect of changing resistance on the current in a circuit

Describe the qualitative variation of resistance of light-dependent resistors (LDRs) with illumination and thermistors with temperature

Know that lamps and LEDs can be used to indicate the presence of a current in a circuit

Know and use voltage = current × resistance, V = IR.

Know that current is the rate of flow of charge

Know and use charge = current × time, Q = It.

Know that electric current in solid metallic conductors is a flow of negatively charged electrons

Understand why current is conserved at a junction in a circuit

Know that the voltage across two components connected in parallel is the same

Calculate the currents, voltages and resistances of two resistive components connected in a series circuit

Know that:

• voltage is the energy transferred per unit charge passed
• the volt is a joule per coulomb

Know and use energy transferred = charge × voltage, E = QV.