Physics 9702 · AS & A Level · Potential difference and power
Potential difference and power — practice question
A battery is joined in series with resistors X and Y, as illustrated in Fig. 6.1. X has a fixed resistance, whereas Y has resistance $6.0\,\Omega$. The battery has electromotive force (e.m.f.) $24\,\text{V}$ and zero internal resistance. A variable resistor with resistance $R$ is connected in parallel with X. The battery current $I$ is altered by changing $R$ from $5.0\,\Omega$ to $20\,\Omega$. Fig. 6.2 shows how $I$ changes with $R$.
(a)[1]
Explain why the potential difference (p.d.) between A and C remains $24\,\text{V}$ for every value of $R$.
(b)[2]
Use Fig. 6.2 to state and explain how the p.d. across resistor Y changes as $R$ is increased. You do not need to give numerical values.
(c)
For $R = 6.0\,\Omega$ :
(c(i))[2]
Demonstrate that the p.d. between A and B is $9.6\,\text{V}$.
(c(ii))[3]
Calculate the resistance of X.
(c(iii))[2]
Calculate the power delivered by the battery.
(d)[1]
State and explain qualitatively how the power provided by the battery changes when the resistance $R$ is increased.
Worked solution & mark scheme
This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: “No lost volts / no energy dissipated in the battery or internal resistance” …