Question

an equipotential surface that surrounds a +3.0uCuC point charge has a radius of 2.0cm. what is the potential of this surface?

Answer 1

Explanations & Calculations

• Potential of that surface is the energy needed to take a positive unit charge from infinity (where the potential is zero) to that point under the influence of the given charge (which causes any potential at that point.
• Thus the potential at that point is what just given by the standard equation $\small V=k\large\frac{q}{r}$

• Therefore substituting the available values with units correctly, the potential can be calculated.

$\qquad\qquad \begin{aligned} \small V&=\small (9\times10^9Nm^2C^{-1})\times\frac{3.0\times10^{-6}C}{0.02m}\\ &=\small 1.35\times10^6\,Nm^{-1}C^{-1}\,\,or\,\,1.35\times10^6JC^{-1}\,\,or\,\,1.35\times10^{6}V \end{aligned}$