Electrostatics Question 64
The capacitance of an air capacitor is $ 15\mu F $. The separation between the parallel plates is $ 6mm $. A copper plate of $ 3mm $ thickness is introduced symmetrically between the plates. The capacitance now becomes [MP PMT 1995]
Options:
A) $ 5\mu F $
B) $ 7.5\mu F $
C) $ 22.5\mu F $
D) $ 30\mu F $
Show Answer
Answer:
Correct Answer: D
Solution:
By using $ C _{air}=\frac{{\varepsilon _{0}}A}{d}, $
$ C _{medium}=\frac{{\varepsilon _{0}}A}{d-\frac{t}{K}+\frac{t}{K}} $
For K = ¥ $ C _{medium}=\frac{{\varepsilon _{0}}K A}{d-t} $
therefore $ \frac{C _{m}}{C _{a}}=\frac{d}{d-t} $
therefore $ \frac{C _{m}}{15}=\frac{6}{6-3} $
therefore $ C _{m}=30\mu C $
BETA
