Question

47. A highly conducting sheet of aluminium foil
of negligible thickness is placed between the
plates of a parallel plate capacitor. The foil
is parallel to the plates. If the capacitance
before the insertion of foil was 10 u F, its
value after the insertion of foil will be
1) 20 u F 2) 10 uF 3) 5 u F 4) Zero
​

Answer 1

Answer:

Initial capacitor C=

d

ϵ

0

A

=10μR

After inserting aluminium foil the effective capacitor is series combination of C

1

=C

2

=

2

d

ϵ

0

A

∴

C

eff

1

=

C

1

1

+

C

2

1

⇒C

eff

=

2

C

1

⇒C

eff

=

d

ϵ

0

A

⇒C

eff

=10μF

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