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.
Practise AQA GCSE Physics Current, potential difference and resistance with exam-style questions for Foundation and Higher tier. 82 questions covering Standard circuit diagram symbols, Electrical charge and current, Current, resistance and potential difference, and Resistors, matched to the AQA GCSE Physics (8463) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.