Question

A parallel plate capacitor with air between the plates has a capacitance of 10 pF. The capacitance, if the distance between the plates is reduced by half and the space between them is filled with a substance of dielectric constant 4 is.

• A. 80 pF
• B. 96Pf
• C. 100pF
• D. 120 Pf

Answer 1

Answer: (A)

80 pF

Answer 2

: Here,$C_{1} = \frac{\varepsilon_{o}A}{d} = 10pF$ …(i)

and $C_{2} = K\frac{\varepsilon_{o}A}{d/2} = \frac{4 \times 2\varepsilon_{o}A}{d}$ ($\because$K= 4)

$= 8 \times 10$ (using (i))

= 80 pF