A portable laser fluorometer, used to detect photosynthetic microalgae in field water samples, is powered by a rechargeable lithium-ion battery pack.
Write down the equation which links charge flow (QQQ), current (III), and time (ttt).
The fluorometer was operated continuously for 25,000 s25,000\text{ s}25,000 s before the battery pack required recharging. During this period, the average current through the laser diode was 75 mA. Calculate the total charge flow through the laser diode.
During a routine maintenance check, the battery pack was reinstalled with reversed polarity. Explain why the laser diode did not emit light.
Write down the equation which links efficiency, total power input, and useful power output.
The total electrical power input to the laser diode during normal operation was 0.28 W. The optical efficiency of the diode was 0.75. Calculate the useful optical 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.