A resistor with resistance $R$ is joined across a cell of electromotive force (e.m.f.) $E$ and negligible internal resistance. Which one alteration to the circuit would produce the greatest rise in the power dissipated in the resistor?
- Adoubling the value of $E$
- Bdoubling the value of $R$
- Chalving the value of $E$
- Dhalving the value of $R$