(a)[1]
Define electromotive force (e.m.f.) of a cell.
(b)
A cell C with e.m.f. $1.50\,\text{V}$ and internal resistance $0.200\,\Omega$ is connected in series with resistors X and Y, as shown in Fig. 7.1. X has a fixed resistance, while Y can be adjusted.
(b(i))[3]
The resistance of Y is changed from $0$ to $8.00\,\Omega$. State and explain how the potential difference (p.d.) between points A and B (terminal p.d. across C) changes. Numerical values are not needed.
(b(ii).1)[2]
The resistance of Y is adjusted to $6.00\,\Omega$. The current in the circuit is $0.180\,\text{A}$. Calculate the resistance of X.
(b(ii).2)[2]
Calculate the potential difference between points A and B.
(b(ii).3)[2]
Calculate the cell efficiency.