OCR GCSE Physics: Electricity

A student builds two circuits from identical cells and identical lamps. In Circuit A the two lamps are connected in series; in Circuit B the two lamps are connected in parallel. The same battery is used in each.

Describe and explain how the current, the potential difference across each lamp, and the total resistance compare between the series circuit and the parallel circuit. Explain which circuit makes the lamps brighter and why. (6 marks)

A component in a circuit has a charge of 240 C passing through it in a time of 2.0 minutes.

(a) Calculate the current through the component. Use $Q = It$Q=It (convert the time to seconds first). Show your working and give the unit. (2 marks)

(b) The potential difference across the component is 6.0 V. Calculate its resistance. Use $V = IR$V=IR. (2 marks)

An electric heating element has a resistance of 24 $\Omega$Ω and a current of 5.0 A passes through it when it is switched on.

Calculate the power of the heating element. Use $P = I^2R$P=I2R. Show your working and give the unit. (3 marks)

A microwave oven has a power rating of 900 W. It is switched on for 5.0 minutes to heat some food.

(a) Calculate the energy transferred by the microwave oven. Use $E = Pt$E=Pt (convert the time to seconds first). Show your working and give the unit. (2 marks)

(b) State the energy transfer taking place, naming the useful energy store the electrical energy is transferred to. (1 mark)

A three-pin plug used for mains appliances in the UK contains a live wire, a neutral wire and an earth wire, together with a fuse.

Explain the job of the earth wire and the fuse, and how they work together to keep the user safe if a fault connects the live wire to a metal case. (2 marks)

Mains electricity in the UK is supplied as alternating current (a.c.), whereas a battery supplies direct current (d.c.).

State the difference between alternating current and direct current. (1 mark)