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$2 \times 10^{-7} \;C$ અને $3 \times 10^{-7} \;C$ વિદ્યુતભાર ધરાવતા અને એકબીજાથી હવામાં $30 \,cm$ અંતરે રહેલા બે વિદ્યુતભારિત ગોળાઓ વચ્ચે કેટલું બળ લાગે?
$3 \times 10^{-4}\; N$
$6 \times 10^{-3}\; N$
$8 \times 10^{-2}\; N$
$1 \times 10^{-3}\; N$
Solution
Repulsive force of magnitude $6 \times 10^{-3} \,N$
Charge on the first sphere, $q_{1}=2 \times 10^{-7} \,C$
Charge on the second sphere, $q_{2}=3 \times 10^{-7} \,C$
Distance between the spheres, $r=30 \,cm =0.3\, m$
Electrostatic force between the spheres is given by the relation
$F=\frac{1}{4 \pi \varepsilon_{0}} \cdot \frac{q_{1} q_{2}}{r^{2}}$
Where, $\varepsilon_{0}=$ Permittivity of free space and $\frac{1}{4 \pi \varepsilon_{0}}=9 \times 10^{9} \,Nm ^{2} \,C ^{-2}$
Therefore, force
$F =\frac{9 \times 10^{9} \times 2 \times 10^{-7}}{(0.3)^{2}}=6 \times 10^{-3} \,N$
Hence, force between the two small charged spheres is $6 \times 10^{-3}\; N$. The charges are of same nature. Hence, force between them will be repulsive.
