Question 9

Explain what would happen if in the capacitor given in Exercise 2.8, a 3 mm thick mica sheet (of dielectric constant = 6) were inserted between the plates,

(a) While the voltage supply remained connected.

(b) After the supply was disconnected.

Answer

(a) Dielectric constant of the mica sheet, *k* = 6

Initial capacitance, C = 1.771 × 10 ^{-11} F

New Capacitance, *C*'= *kC*= 6x1.771x10^{-11} =106 pF

Supply voltage, *V* = 100 *V*

New Charge, *q'*=*C'V*=6x1.771x10^{-9 }=1.06x 10^{-8} C

Potential across the plates remains 100 V

(b) Dielectric constant, *k* = 6

Initial capacitance, C = 1.771 × 10^{-11} F

New Capacitance,* C*'= *kC*= 6x1.771x10^{-11} =106 pF

If supply voltage is removed, then there will be no effect on the amount of charge in the plates.

Charge = 1.771 × 10^{- 9} C

Potential across the plates is given by,

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