Question

Two small conducting spheres of equal radius have charges $+ 10\mu C$ and $- 20\mu C$ respectively and placed at a distance $R$ from each other experience force$F_{1}$. If they are brought in contact and separated to the same distance, they experience force$F_{2}$. The ratio of $F_{1}$ to $F_{2}$ is

• A. 1 : 8
• B. – 8 : 1
• C. 1 : 2
• D. – 2 : 1

Answer 1

Answer: (B)

– 8 : 1

Answer 2

$F \propto Q_{1}Q_{2}$ ⇒ $\frac{F_{1}}{F_{2}} = \frac{Q_{1}Q_{2}}{Q_{1}^{'}Q_{2}^{'}} = \frac{10 \times - 20}{- 5 \times - 5} = - \frac{8}{1}$