A radio transmitter is tested at a constant potential difference of 30 V. Its current is recorded during two consecutive operating periods.
| Operating period | Current | Time |
|---|---|---|
| First | 1.2 A | 90 s |
| Second | 0.40 A | 30 s |
Use E=IVtE=IVtE=IVt. Which constant power would transfer the same total energy as the transmitter transfers during this 120 s test?
30 W30\ \mathrm{W}30 W
36 W36\ \mathrm{W}36 W
12 W12\ \mathrm{W}12 W
24 W24\ \mathrm{W}24 W
105 exam-style questions on Edexcel GCSE Physics 10.3 Electrical energy and power, covering 10.3.1 The heating effect of an electric current, 10.3.2 Reducing energy transfer in wires, 10.3.3 Advantages and disadvantages of the heating effect, 10.3.4 Energy transferred by an electrical circuit, 10.3.5 Electrical power, and 10.3.6 Energy transfers in domestic devices. Each one has a worked solution and a mark scheme showing where the marks go.