Question
Concentric equipotential surfaces due to a charged body placed at the centre are shown. Identify the polarity of the charge and draw the electric field lines due to it.
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Answer
For a single charge the potential is given by $\text{V}=\frac{1}{4\pi\varepsilon_0}\frac{\text{q}}{\text{r}}$This shows that V is constant if r is constant. Greater the radius smaller will be the potential. In the given figure, potential is increasing. This shows that the polarity of charge is negative (-q). The direction of electric field will be radially inward. The field lines are directed from higher to lower potential.
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