2 Electricity

2.1

Use the following units: ampere (A), coulomb (C), joule (J), ohm (Ω), second (s), volt (V) and watt (W)

Understand how the use of insulation, double insulation, earthing, fuses and circuit breakers protects the device or user in a range of domestic appliances

Understand why a current in a resistor results in the electrical transfer of energy and an increase in temperature, and how this can be used in a variety of domestic contexts

Know and use power = current × voltage, P = IV, and apply it to selecting appropriate fuses.

Use energy transferred = current × voltage × time, E = IVt.

Know the difference between mains electricity being alternating current (a.c.) and direct current (d.c.) being supplied by a cell or battery

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.

Identify common materials that are electrical conductors or insulators, including metals and plastics

Practical: investigate how insulating materials can be charged by friction

Explain how positive and negative electrostatic charges are produced on materials by the loss and gain of electrons

Know that there are forces of attraction between unlike charges and forces of repulsion between like charges

Explain electrostatic phenomena in terms of the movement of electrons

Explain the potential dangers of electrostatic charges, e.g. when fuelling aircraft and tankers

Explain some uses of electrostatic charges, e.g. in photocopiers and inkjet printers