﻿ Two parallel-plate capacitors X and Y have the same area of plat

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## CBSE Class 12 Physics Solved Question Paper 2016

1.

A point charge +Q is placed at point O as shown in the figure. Is the potential
difference VA – VB is positive, negative or zero?

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2. How does the electric flux due to a point charge enclosed by a spherical Gaussian surface get affected when its radius is increased?
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3. Write the underlying principle of a moving coil galvanometer.
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4. Why are microwaves considered suitable for radar systems used in aircraft navigation?
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5. Define 'quality factor' of resonance in a series LCR circuit. What is its SI unit?
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6. Two cells of emfs 1.5 V and 2.0 V,  having internal resistances 0.2 Ω and 0.3 Ω, respectively, are connected in parallel. Calculate the emf and internal resistance of the equivalent cell.
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7. A charge is distributed uniformly over a ring of radius 'a'. Obtain an expression for the electric intensity E at a point on the axis of the ring. Hence, show that for points at large distance from the ring, it behaves like a point charge.
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8.

a) Write the expression for the magnetic force acting on a charged particle moving with velocity v in the presence of magnetic field B.

b) A neutron, an electron and an alpha particle, moving with equal velocities, enter a uniform magnetic field going into the plane of paper, as shown. Trace their paths in the field and justify your answer.

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9.

i) Define mutual Inductance.

ii) A pair of adjacent coils has a mutual inductance of 1.5 H. If the current in one coil changes 20 A in 0.5 s, what is the change of flux linkage with the other coil?

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# 10.Two parallel-plate capacitors X and Y have the same area of plates and same separation between them. X has air between the plates, while Y contains a dielectric medium of i) Calculate capacitance of each capacitor if the equivalent capacitance of the combination is 4 ii) Calculate the potential difference between the plates x and Yiii) Estimate the ratio of electrostatic energies stored in x and Y

i)

Capacitance of a parallel plate capacitor is given by,

ii)

Potential difference between plates X and Y can be calculated as,

Q = CV

iii)

The ratio of electrostatic energies can be calculated as:

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