Question

Deduce the effect of introducing dielectric slab between plates of parallel plate capacitor on the capacitance of a parallel plate capacitor?

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12th

Physics

Electrostatic Potential and Capacitance

Effects of Dielectrics in Capacitors

Derive the expression for t...

PHYSICS

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Asked on October 15, 2019 by

Jeya Sajeev

Derive the expression for the capacitance of a parallel plate capacitor.

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VIDEO EXPLANATION

ANSWER

Let d be the separation of two conducting parallel plates , each of area A .

If charge q is given to first plate , then charge −q is induced on inner surface of second plate and charge +q induced on the outer surface , is earthed .

Now , the electric field between the two plates will be ,

E=V/d

or V=Ed ...........eq1

If σ is he surface density of the plates , then the electric field between two plates is given by ,

E=σ/ε

0

...............eq2

where ε

0

= absolute permittivity of the free space.

Putting the value of E from eq2 to eq1 , we get

V=

ε

0

σ

d ................eq3

but we have ,

σ=q/A

hence , V=

ε

0

A

qd

Now , capacitance of parallel capacitor ,

C=

qd/ε

0

A

q

or C=

d

ε

0

A