Question

Two charged particles having charge $2\times {10}^{-8}C$ each are joined by an insulating string of length $100cm$. The system is kept on a horizontal table. Find the tension in the string.

• A. $3.6\times {10}^{-7}N$
• B. $3.6\times {10}^{-6}N$
• C. $3.6\times {10}^{-4}N$
• D. $3.6\times {10}^{-5}N$

Answer 1

The correct option is B $3.6\times {10}^{-6}N$

Tension in string is equal to the force by which two charges repel each other.

$q_1=q_2=2\times {10}^{-8}C$ and $r=100cm=1m$

$T=F_e=\frac{q_1{q}_2}{4\pi {ϵ}_o{r}^2}$

$⟹T=9\times {10}^9\times \frac{4\times {10}^{-16}}{1^2}$

$⟹T=36\times {10}^{-7}N$

$⟹T=3.6\times {10}^{-6}N$

Answer-(B)