A precision laser-diode alignment pointer is powered by rechargeable cells connected in series.
Write down the equation which links charge flow (QQQ), current (III), and time (ttt).
The laser-diode pointer operated continuously for 15 000 s15\,000\text{ s}15000 s before the cells required recharging. The current passing through the laser diode during this time was 65 mA65\text{ mA}65 mA. Calculate the total charge flow through the laser diode.
After recharging, the cells were reinstalled into the pointer the wrong way around. Explain why the laser diode did not work.
Write down the equation which links efficiency, total power input, and useful power output.
The total power input to the laser diode was 0.80 W0.80\text{ W}0.80 W. The efficiency of the laser diode in producing light was 0.650.650.65. Calculate the useful power output of the laser diode.
39 exam-style questions on AQA GCSE Physics 2.1 Current, potential difference and resistance, covering 2.1.1 Standard circuit diagram symbols, 2.1.2 Electrical charge and current, 2.1.3 Current, resistance and potential difference, and 2.1.4 Resistors. Each one has a worked solution and a mark scheme showing where the marks go.