Question

Two identical conducting spheres having unequal positive charges $q_1$ and $q_2$ separated by distance $r$. If they are made to touch each other and then separated again to the same distance. The electrostatic force between the spheres in this case will be (neglect induction of charges)

• A. More than before
• B. Less than before
• C. Zero
• D. Same as before

Answer 1

The correct option is A More than before

Step 1: Calculate initial force

Let the distance between the spheres is $r$ Then,

$F\propto \frac{q_1{q}_2}{r^2}$

Step 2 : Calculate final force

When the identical spheres are joined, their charge gets averaged

$\Rightarrow q_1^{\prime }=q_2^{\prime }=\frac{q_1+q_2}{2}$

or

$F\propto \frac{(q_1+q_2{)}^2}{4r^2}>\frac{q_1{q}_2}{r^2}$

Final answer:(c)