# Q 1.1: What is the force between two small charged spheres having charges of $2 \times 10^{-7}$C and $3 \times 10^{-7}C$ placed 30 cm apart in air?

Given,

$q_{1}$ =  $2 \times 10^{-7}$ C

$q_{2}$ =  $3 \times 10^{-7}C$

r = 30 cm = 0.3 m

We know,

Force between two charged particles, $q_{1}$  and $q_{2}$ separated by a distance r.

$F = \frac{1}{4\pi \epsilon _{0}} \frac{q_{1}q_{2}}{r^2}$

$= \frac{1}{4\pi \epsilon _{0}} \frac{2\times10^{-7} \times 3 \times 10^{-7}}{(30\times10^{-2}\ m)^2\ }$

$= (9\times10^9\ N)\times \frac{6\times10^{-14+4}}{900\ m^2\ } = 6\times10^{-3} N$

Since, the charges are of same nature, the force is repulsive.

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