Question

Two identical metal spheres possess $+60C$ and $-20C$ of charges. They are brought in contact and then separated by $10cm$. The force between them is:

• A. $36\times {10}^{13}N$
• B. $36\times {10}^{14}N$
• C. $36\times {10}^{12}N$
• D. $3.6\times {10}^{12}N$

Answer 1

The correct option is A $36\times {10}^{13}N$

Since the spheres are identical, when brought in contact, the net charge is distributed equally between them.

The net charge $=40C(=60C-20C)$.

Thus, each sphere gets $20C$ charge.

Applying Coulomb's law:
$F=\frac{1}{4\pi {\epsilon }_o}\frac{Q_1{Q}_2}{r^2}$, where $Q_1=Q_2=20C$ and $r=0.1m$

$\Rightarrow$ $F=36\times {10}^{13}N$.