A vacuum-insulated parallel-plate capacitor with plate separation dhas capacitance C0. What is the capacitance if an insulator with dielectric constant κand thickness d/2is slipped between the electrodes without changing the plate separation?

Short Answer

Expert verified

If an insulator with dielectric constant κand thickness d/2is slipped between the electrodes without changing the plate separation then the capacitance is Cs=2κC0κ+1

Step by step solution

01

Given Information

Parallel-plate capacitor with plate separation =d

Capacitance=C0

Dielectric constant=k

Thickness=d/2

02

Explanation

If we insert an insulator into such a capacitor with separation dand k=1, then we can treat it as two capacitors connected in series, each with thickness d/2and κ=1

It is clear that the capacitance of the air half will be

C1=2C0

Since the capacitance is given as

C=ε0κAd.

The capacitance of the other half will then clearly be

C2=2κC0.

Resulting capacitance of the considered system will be

Cs=12C0+12κC0-1=κ+12κC0-1

The resulting capacitance will be

role="math" localid="1648714430037" Cs=2κC0κ+1

03

Final Answer

Hence, the capacitance is Cs=2κC0κ+1.

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