NEB Class 12 Science Physics Question Paper 2080 (Set B)

If L represents linear momentum, I represents moment of inertia, then $\dfrac{L^2}{2I}$ is

What is moment of inertia of a solid sphere?

For a body undergoing rotational motion, its radius of gyration depends on

If one mole of an ideal gas at STP is heated through 1K, work done by gas in heat unit will be

Which of the following is a universal constant?

Velocity of sound in gas is independent of

The ratio of sound in hydrogen gas $\left(\gamma = \dfrac{7}{5}\right)$ to that in Helium gas $\left(\gamma = \dfrac{5}{3}\right)$ at the same temperature is

In which one of the following diagrams the currents are related by the equations $I_1 - I_2 = I_3 - I_4$?

Each option is a junction diagram of four currents $I_1, I_2, I_3, I_4$:

• a)
• b)
• c)
• d)

When the current flowing in a circular coil is doubled and the number of turns of the coil in it is halved, the magnetic field at its center will become

The galvanometer has resistance of 25Ω and has maximum current can be passed through it 0.01A. In order to change into an ammeter of range 10A, the shunt required is

If the frequency of light in a photoelectric experiment is doubled, the stopping potential will be

Suppose that only two external forces act on rigid body and two forces are equal in magnitude but opposite in direction. Under what condition will the body rotate?

If the earth contracts to half its radius, what would be the length of the day?

a. State principle of conservation of angular momentum? (1)

b. A disc of moment of inertia $5\times10^{-4}\,\text{kg m}^2$ is rotating freely about the axis through its center at 40 rpm. Calculate the new revolution per minute if some wax of mass 0.02 kg is dropped gently on the disc 0.08 m from the axis. (3)

c. On what factor does moment of inertia depend? (1)

a. How can you justify first law of thermodynamics obeys principle of conservation of energy? (1)

b. If a thermodynamic process starts from A and comes to A using path 1 and 2 as shown by arrows, does the net work done become zero? If not explain. (See PV diagram showing a cyclic process A→A via paths 1 and 2.)

c. In adiabatic process, no heat is exchanged but work is done, does it mean that adiabatic process violates first law of thermodynamics? (2)

Study the given progressive wave (a graph of a transverse wave from O to A with amplitude 'a' shown).

a. What is 'a' named? (1)

b. If the wave travels from O to A in 2s, find the frequency of the wave. (2)

c. For a=π, find the maximum particle velocity for given condition in b. (2)

In a current carrying circular coil,

a. What is the magnetic field at a point on the axis of coil where the point is at distance 'x' from centre of coil whose radius is 'a'? (1)

b. What would be the magnetic field at centre and axis distance $\dfrac{a}{2}$ from centre where 'a' is radius of circular coil. (2)

c. Why perpendicular components of field on axis are not considered in calculation of net magnetic field? (2)

Show the direction of motion of charge particle in uniform magnetic field for the following cases. Also, write the force experienced by charge particles in each of cases:

a. A negative charge particle enters a field acted perpendicularly inward to plane of paper. (2)

b. A positive charge particle enters the field acting perpendicularly outward from plane of paper. (2)

c. If any charge particle moves parallel or antiparallel to magnetic field. (1)

a. What is cross field? What is the speed of electron in a cross field when to magnetic field intensity 'B' is same region simultaneously. (1+1)

b. In a Thomson experiment, voltage across the plates is 50V and distance between them is 3cm. The magnetic field applied to make the beam undeflected is $10^{-4}$ T, what is the velocity of electron passing between the plates. (3)

a. What is threshold frequency? Does it depend upon the intensity of incident light? (1+1)

b. Discuss Einstein's photoelectric equation. (3)

The speed of sound derived from Newton's formula was corrected by Laplace to determine correct value of speed of sound.

a. What thermodynamic process did Laplace assume to overcome the discrepancy of Newton's formula? What mechanism occurred in gas during propagation of sound? Describe. (3)

b. Describe the expression for Laplace correction of speed of sound. (3)

c. At what temperature, the speed of sound is increased by 50% than that at 27°C? (2)

OR

a. Differentiate wave front and wavelet? (1)

b. Can Snell's law be verified from wave theory? Explain with figure only. (3)

c. Prove the laws of reflection of light using wave theory of light. (4)

a. State Wheat Stone bridge principle. (1)

b. Deduce Wheatstone bridge principle for balanced condition. (3)

c. In the adjacent circuit find:

i. the current in resistor R (1)

ii. resistance R (1)

iii. unknown emf ε (1)

iv. if the circuit is broken at P, what is the current in resistor R? (1)

a. The value of $\dfrac{e}{m}$ is constant for cathode rays but not for positive rays, why? (2)

b. What is quantization of charge? Describe the theory of Millikan's oil drop experiment to determine the number of charges on an oil drop? (1+3)

c. An ion for which the charge per unit mass is $4.40\times10^{7}$ C/kg has velocity of $3.52\times10^{5}$ m/s and moves in a circular orbit in magnetic field of flux density 0.4T. What will be the radius of this orbit? (2)