Question

What happens to the force between two charged particles when they are moved $50$% closer to one another?

• A. The force between them doubles
• B. The force between them halves
• C. The force between them remains the same
• D. The force between them reverses
• E. The force between them operates in the same direction

Answer 1

The correct option is E The force between them operates in the same direction

Let the initial distance between the two charges be $r$.

$\therefore$ Force between them $F=\frac{K{Q}_1{Q}_1}{r^2}$

Now they are moved closer, thus new distance between them $r^{\prime }=\frac{r}{2}$

New force $F^{\prime }=\frac{K{Q}_1{Q}_2}{(r/2{)}^2}=4F$

Thus the force between them becomes $4$ times the initial force.

Force between two charges always act along the line of the two charges. Hence, the direction of force does not change.