Question

A solid conducting sphere has a positive charge. A nearby electron experiences a force due to the electric field produced by the solid conducting sphere.
What direction is this force?

• A. Toward the sphere.
• B. In a circular path perpendicular to the E-field.
• C. Away from the sphere.
• D. The direction of the force cannot be determined without also knowing the direction of the velocity of the electron.

Answer 1

Answer: (A)

Toward the sphere.

The electric field outside the positively charge q conducting sphere is $\overrightarrow{E}=\frac{kq}{r^2}\hat{r}$. So the field outside the sphere

is radially outward.

As electron has charge $(-e)$, so the force on electron due to field E will be $\overrightarrow{F}=-e\overrightarrow{E}$

Thus, the negative sign indicates that the force F will act toward the sphere.