Question

Two small conducting sphere of equal have charges $10\mu C$ and $-20\mu C$ are placed at a distance ${}^{\prime }{R}^{\prime }$ from each other experience force $F_1$. If the 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

The correct option is B $-8:1$

The charges $=10\mu C$ and $-20\mu C$

distance $=R$

force $=F_1$

experience force $F_2$

$F_1=\frac{K^{-10}\times 20}{R^2}$

$F_2=+K\times \frac{50\times 30}{R^2}$ $\frac{10\times 20}{400}$

$\frac{F_1}{F_2}=\frac{-10\times 20}{25}$ $\frac{200}{25}$

$F_1:F_2=-8:1$