Question

Two identical charges repel each other with a force equal to $10\, mgwt$ when they are $0.6\, m$ apart in air.$( g = 10 ms^{-2} )$ The value of each charge is

• A. 2 mc
• B. $2 \times 10^{-7}\,C$
• C. 2 nc
• D. $2 \mu C$

Answer 1

Answer: (D)

$2 \mu C$

Answer 2

Coulomb force is given by
$F= \frac{1}{4 \pi \varepsilon_{0}} \frac{q_{1} q_{2}}{r^{2}}$
$\therefore\left(10 \times 10^{-3}\right) \times 10= \frac{\left(9 \times 10^{9}\right) \times q^{2}}{(0.6)^{2}}$
$\left[\because q_{1}=q_{2}=q\right]$
or $q^{2} =\frac{10^{-1} \times 0.36}{9 \times 10^{9}}$
$=4 \times 10^{-12}$
$q =2 \times 10^{-6} \,C$
$=2 \,\mu \,C$