Q106 / 180 · AIIMS 2014 · Physics
The diameter of the plate of a parallel plate condenser is $6 \mathrm{~cm}$. If its capacity is equal to that of a sphere of diameter $200 \mathrm{~cm}$, the separation between the plates of the condenser is
- A$4.5 \times 10^{-4} \mathrm{~m}$
- Correct answerB$2.25 \times 10^{-4} \mathrm{~m}$
- C$6.75 \times 10^{-4} \mathrm{~m}$
- D$9 \times 10^{-4} \mathrm{~m}$
Solution
As $\frac{\varepsilon_0 A}{d}=4 \pi \varepsilon_0 R$
$d=\frac{A}{4 \pi R}=\frac{\pi(6 / 2)^2}{4 \pi(100)}=2.25 \times 10^{-2} \mathrm{~cm}$
$=2.25 \times 10^{-4} \mathrm{~m}$
Hence, the correct answer is option: 'B'.