Question

Two copper spheres, $A$ and $B$, are identical in all respect but A carries a charge of $-3\mu C$ whereas $B$ Is charged to $+1\mu C$. The two spheres are brought together until they touch and then separated by some distance. Which of the following statements is true concerning the electrostatic force $F$ between the spheres?

• A. $F=0$ as one of the spheres is uncharged
• B. $F=0$ as both the spheres are uncharged
• C. $F$ is attractive
• D. $F$ is repulsive.

Answer 1

The correct option is D $F$ is repulsive.

Charge on $A^{+}$ sphere $=-3$ $uC$

Charge on $B$ sphere $=+1$ $uC$

When they are connected the charge get redistributed, i.e.

$\Rightarrow$ Charge on both sphere $=\frac{-3+1}{2}$ $uC=-1$ $uC$

So charge on either sphere $=-1$ $uC$

Therefore, After connecting charge on sphere $A=-1$ $uC$

After connecting charge on sphere $B=-1$ $uC$

Therefore, there will be a repulsive force between the sphere because of like charges.