A small local generator supplies electricity to a community at a potential difference of 12,000 V12,000\text{ V}12,000 V.
The energy transferred by the generator in one second is 360,000 J360,000\text{ J}360,000 J.
Calculate the charge flow from the generator in one second. Use the equation:
charge flow=energypotential difference \text{charge flow} = \frac{\text{energy}}{\text{potential difference}} charge flow=potential differenceenergyThe electricity supply is stepped down to 240 V for use in a workshop. The table below shows the current in some machines in the workshop when running:
| Machine | Current (A) |
|---|---|
| Lathe | 8.20 |
| Drill | 1.50 |
| Sander | 2.30 |
Calculate the total power of all these machines running at the same time. Use the equation:
power=potential difference×current \text{power} = \text{potential difference} \times \text{current} power=potential difference×current44 exam-style questions on AQA GCSE Physics 1.1 Energy changes in a system, and the ways energy is stored before and after such changes, covering 1.1.1 Energy stores and systems, 1.1.2 Changes in energy, 1.1.3 Energy changes in systems, and 1.1.4 Power. Each one has a worked solution and a mark scheme showing where the marks go.