Physics XII - Electric Potential 02

Question : 1

(skipped)

A capacitor of capacity C is charged to a potential V. Electrostatic potential energy stored in the electric field inside the capacitor is

Options:

	CV2
	Zero

Solution :

(B)

Energy in capacitor  

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Question : 2

(skipped)

A parallel plate capacitor is charged, such that electrostatic potential energy in it is U. Now the plates of capacitor are pulled apart to double their separation. New potential energy in the isolated capacitor is

Options:

	U
	2U
	4U

Solution :

(C)

Initial energy  

Now plate separation is doubled, so new capacity  

Capacitor is isolated so magnitude of charge on plates remain unchanged, therefore new energy

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Question : 3

(skipped)

A capacitor of capacity 2 μF is charged to 10 V by a battery. The total work done by the battery during this process is

Options:

	2 × 10–4 J
	2 × 10–6 J
	2 × 10–3 J
	10–4 J

Solution :

(A)

Work done by battery

W = CV² = 2 × 10^–6 F × (10 V)²

     = 2 × 10^–4 J

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Question : 4

(skipped)

In the given figure, two identical capacitors C₁ and C₂ are joined in parallel across a battery of emf V. Electrostatic potential energy at steady state in capacitor C₁ is U, then electrostatic potential energy in the capacitor C₂ is

                

Options:

	U
	2 U
	Zero

Solution :

(A)

Both capacitors are at same potential difference.

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Question : 5

(skipped)

A spherical capacitor (air filled) is charged to electrostatic potential energy U. Air is present outside the outer shell. Now the capacitor is dipped in water (dielectric constant = K). New potential energy of the isolated spherical capacitor is

Options:

	U K
	U
	Zero

Solution :

(C)

Presence of dielectric outside the outer shell does not affect the capacity of the spherical capacitor.

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Question : 6

(skipped)

Electrostatic potential energy stored in the 20 μF. Capacitor at steady state in the figure shown is

                                 10 μF                                       20 μ F

                                                          30 V

Options:

	10–3 J
	5 × 10–4 J
	2 × 10–3 J
	5 × 10–3 J

Solution :

(A)

P.D. across 20 μF,

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Question : 7

(skipped)

Two capacitors of capacity 10 μF and 20 μF are connected in parallel across 10 V battery till these capacitors attain a steady state. Now they are disconnected from battery and connected across each other, such that their dissimilar plates are connected. Common potential of these capacitors at steady state is

Options:

	Zero
	10 V

Solution :

(B)

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Question : 8

(skipped)

Out of two identical capacitors, a capacitor is uniformly filled with a dielectric of dielectric constant K and kept uncharged. Another capacitors is charged to potential V. Now these capacitors are connected across each other such that their common potential is . Dielectric constant of the dielectric is

Options:

	3
	4
	1
	2

Solution :

(D)

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Question : 9

(skipped)

Two capacitors of capacity 10 μF and 15 μF are charged to 15 V and 10 V respectively. If they are connected across each other with their similar polarities, then loss of electrostatic potential energy is

Options:

	75 μJ
	150 μJ
	37.5 μJ
	100 μJ

Solution :

(A)

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Question : 10

(skipped)

In the adjoining figure, if electrostatic potential energy in capacitor A is U, then electrostatic potential energy in capacitor C is

      

Options:

	U
	2 U
	4 U

Solution :

(B)

P.D. across A and C are equal.