Class 12 Physics Model Question Set A

Define angular momentum. Write its SI unit.

The speed of a motor engine decreases from 900 rev/min to 600 rev/min in 10 seconds. Calculate:

i. Angular acceleration
ii. Number of revolutions made by the motor during this interval
iii. How many additional seconds are needed for motor to come to rest in the same rate

For a simple pendulum, show that the acceleration is directly proportional to the displacement of bob from its mean position.

A bob of mass 8 kg performs SHM of amplitude 30 cm. The restoring force is 60 N. Calculate:

i. Time period
ii. Maximum acceleration
iii. Kinetic energy when displacement is 12 cm

What is meant by entropy? Write the first law of thermodynamics in terms of entropy.

Can a room be cooled by leaving the door of an electric refrigerator open? Justify.

A quantity of monoatomic gas at 30°C is compressed suddenly to (8/27)th parts of its initial volume. Find the change in temperature assuming γ = Cp/Cv = 5/3.

State and explain Bohr’s postulates of an atomic model.

i. Calculate the de-Broglie wavelength of a neutron having kinetic energy 150 eV.

ii. A proton and an electron have same K.E., which one has greater de-Broglie wavelength?

Define self inductance of a coil.

A current from A to B is increasing in magnitude. What is the direction of induced current, if any, in the loop as shown in figure? Justify.

Calculate the self inductance of a coil of 100 turns if a current of 2A gives rise to magnetic flux of 5×10⁻³ Weber through the coil.

In Young’s double slit experiment, what changes will you observe in fringe width for the following operations?

i. When experiment is shifted from air to inside water.
ii. When slits width is increased?

What is diffraction of light?

Calculate the width of central diffraction peak on a screen 4 m behind a 0.01 m slit illuminated by 600 nm light source.

How can a spherical wave front be changed into plane wavefront? Draw a diagram to justify your answer.

Apply Huygen’s principle to verify the law of reflection of light.

Using Kirchhoff’s laws of electric circuit, derive an expression for balanced condition of Wheatstone bridge.

Conclude with reason, where the balance point will be shifted, towards A or B, when:

i. Resistance R is increased, keeping all other parameters constant.

ii. Resistance S is decreased, keeping R constant.

Define an organ pipe.

What is the ratio of length of two pipes, an open organ pipe A and a closed organ pipe B both vibrating in third overtones in resonance? Justify.

In the given figure (i), source of sound (S) and listener (L) are at rest at position 'S' and 'L' respectively. Figure (ii) represents relative motion between source and listener.

Write any two properties of medium which is necessary for the propagation of sound.

Define the term radioactivity.

Two radioactive samples A and B have equal number of atoms initially. Their half lives are 3 hours and 9 hours respectively. Compare their rate of disintegration after 18 hours from start

Develop a relation between half life and decay constant of a radioactive sample.

What percentage of atoms decayed after five half life periods? Justify your answer with calculation.

Two conductors X and Y carrying currents I₁ and I₂ are placed in air at a distance r apart as shown in figure.

Figure shows a rectangular metal frame ABCD placed in a uniform magnetic field of flux density 4.5 × 10⁻³ T.

Define impedance of LCR circuit.

A series LCR circuit is given in figure.

A device is connected across an ac source of voltage V = V₀ sinωt and the current through X is given by:

I = I₀ sin(ωt + π/2)