A cell with electromotive force (e.m.f.) $E$ and internal resistance of $0.50\,\Omega$ is connected to a resistor whose resistance is $4.7\,\Omega$. The greatest power the resistor can dissipate without becoming overheated is $0.50\,\text{W}$. What is the largest value of $E$ so that the resistor does not overheat?
- A$1.4\,\text{V}$
- B$1.5\,\text{V}$
- C$1.7\,\text{V}$
- D$2.9\,\text{V}$