Cell $E$, with electromotive force (e.m.f.) $2\,\text{V}$ and negligible internal resistance, is joined to a uniform resistance wire with resistance $10\,\Omega$ and length $1.0\,\text{m}$. $Z$ is a connection that can be placed at any point along the resistance wire. A galvanometer is linked between $Z$ and point $Q$. A second source of e.m.f. of about $8\,\text{mV}$ is connected between points $P$ and $Q$. The e.m.f. of the second source is found by moving the position of $Z$ until the galvanometer shows zero. Which modification to the circuit would make it possible to obtain a much more accurate value for the e.m.f. of the second source?
- AAdd a resistor of resistance $0.1\,\Omega$ in series with cell $E$.
- BAdd a resistor of resistance $1000\,\Omega$ in series with cell $E$.
- CAdd a resistor of resistance $10\,\Omega$ in series with the new source.
- DAdd a resistor of resistance $800\,\Omega$ in series with the new source.