Question

The capacity of parallel plate capacitor in air and on immersing it into oil is $50\,\mu F$ and $110\,\mu F$ respectively. The dielectric constant of oil is

• A. 0.45
• B. 0.55
• C. 1.1
• D. 2.2

Answer 1

Answer: (D)

2.2

Answer 2

Capacity of parallel plate capacitor of plate area $A$ is
$C=\frac{K \varepsilon_{0} A}{d}$
where $d$ is separation between the plates and $K$ the dielectric constant.
For air, $K=1$
$\therefore C_{A}=\frac{\varepsilon_{0} A}{d}=50\, \mu F$ ... (i)
For oil,
$\therefore C_{o}=\frac{K \varepsilon_{0} A}{d}=110\, \mu F$ ... (ii)
Dividing E (ii) by E (i),
we get $\frac{C_{o}}{C_{A}}=K=\frac{110}{50}=2.2$