Physics 9702 · AS & A Level · Potential difference and power
Potential difference and power — practice question
In Fig. 6.1, a battery is connected with a light-dependent resistor (LDR), two fixed resistors and a voltmeter in the circuit. The battery has an electromotive force (e.m.f.) of $25\,\text{V}$ and negligible internal resistance. The resistors have resistances of $320\,\Omega$ and $240\,\Omega$.
(a(i))[1]
The voltmeter gives a reading of $16\,\text{V}$. Show that the battery current is $0.050\,\text{A}$.
(a(ii))[3]
Calculate the resistance of the LDR from the information given.
(a(iii))[2]
Determine the ratio \[ \frac{\text{power dissipated in the LDR}}{\text{power dissipated in the } 240\,\Omega \text{ resistor}} \] for the circuit shown.
(b)[3]
The light intensity falling on the LDR increases. State and explain the effect on the voltmeter reading.
Worked solution & mark scheme
This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: “The correct calculation is $I = \frac{16}{320} = 0.050\ \text{A}$.” …