Sub. code 1021
NEB — GRADE XII
Set B
Model Question
Class 12 Physics Model Question Set B
The candidates are required to give their answers in their own words as far as practicable. The figures in the margin indicate full marks.
Pass Marks : 32
सबै प्रश्नको उत्तर दिनुहोस् । (Attempt All Questions)
This model question paper is for Class 12 Physics, Set B (subject code 1021), carrying full marks of 75 with a pass mark of 32, to be completed within 3 Hours. Model answers are available for questions that have one — reveal them with a free account (a few reveals) or a paid plan (unlimited).
Group A
Rewrite the correct options of each question in your answer sheet.
When the torque acting upon a system is zero which of the following will be constant?
Force
Linear momentum
Linear momentum
Angular acceleration
A particle executes SHM. Its initial position is the mean position. The kinetic energy of a particle against time period is represented by the curve:
Bernoulli’s Principle is based on the law of conservation of
mass
energy
linear momentum
angular momentum
An ideal gas is taken through series of changes represented in the diagram below. The net work done by the gas at the end of the cycle is equal to
P₁V₁
12 P₁V₁
6 P₁V₁
3 P₁V₁
What is the significance of the Clausius statement of the second law of thermodynamics?
Defines the maximum theoretical efficiency of a heat engine.
States that heat cannot spontaneously flow from a colder object to a hotter object.
Describes the relationship between entropy and the irreversibility of a process
Describes the direction of spontaneous change in an isolated system.
If the source of sound and the listener move in the same direction with same velocity equal to half the velocity of sound, what is the change in frequency?
0%
25%
50%
100%
The given figure represents a wavefront AB moving in air and incident on a plane glass surface XY. Its position after refraction through the glass slab is CD. The refractive index of glass with respect to air will be equal to:
AB/CD
BD/AD
AC/AD
BD/AC
Self inductance of a coil varies as:
Reciprocal of number of turns
Resistance of the coil
Square of number of turns
Magnitude of current flowing
The region of initiation of seismic energy within the earth is called:
Epicenter
Hypocenter
Pole
Optic center
P-waves are:
Longitudinal
Transverse
Electromagnetic
Ultrasonic
Kirchhoff’s voltage law of electrical circuit is based on the principle of conservation of:
Charge
Mass
Energy
Linear momentum
Group B
Define radius of gyration.
Calculate the moment of inertia of a thin uniform rod about an axis passing through its centre and perpendicular to its length.
A physics teacher stands on a freely rotating platform. He holds a dumbbell in each hand of his outstretched arms while a student gives him a push until his angular velocity reaches 1.5 rad/s. When the freely spinning teacher pulls his hands in close to his body, his angular velocity increases to 5.0 rad/s. What is the ratio of his final kinetic energy to initial kinetic energy?
The displacement (y) of a particle executing simple harmonic motion is
y = r sinωt, where r is the amplitude of vibration.
Define amplitude.
Calculate the acceleration of the motion.
If a uniform spring is cut in half, what is the force constant of each half? How would the frequency of half spring differ from that using the same mass and entire spring?
According to Stoke’s law, when a ball of radius r is falling in a viscous fluid, the viscous force produced is equal to F = 6πηrv, where symbols have their usual meanings.
Define coefficient of viscosity.
How can you use this method to determine the coefficient of viscosity of a liquid? Explain
A horizontal pipe of 25 cm² cross section carries water at a velocity of 3 m/s. The pipe feeds into a smaller pipe of cross section 15 cm². Determine the pressure change that occurs on going from the larger diameter pipe to the smaller pipe.
State first law of thermodynamics.
Apply the first law of thermodynamics to relate the two specific heat capacities of a gas i.e. Cₚ − Cᵥ = R
Obtain the efficiency of a heat engine.
The figure shows the variation of thermo emf with the temperature of the hot junction, when the cold junction is at 0°C.
What is thermoelectric effect?
Define θₙ and θᵢ.
What will be the effect on θᵢ if we shift the cold junction to −10°C?
Give one of the applications of such thermocouple.
Biot-Savart law gives the magnitude of magnetic field produced by a current carrying conductor.
State Biot-Savart law.
Use Biot-Savart law to calculate the magnetic field of a circular current carrying coil at its centre
Also determine the direction of the magnetic field in this case.
The given figure shows the first overtone of a stretched string of length l
Define harmonics and overtone
Calculate the frequency of this mode.
If the tension of the string is increased 4 times, what will be the frequency of this mode?
Write down the Newton’s formula for the velocity of sound in a gas medium with its discrepancy
Obtain Laplace’s corrected formula.
Explain why sound waves are also called pressure waves.
When a p-type semiconductor is suitably joined to an n-type semiconductor, a p-n junction is formed.
Describe the formation of potential barrier.
When the p-n junction diode is forward biased, a large current flows, why?
For the digital circuit given below, write the truth table showing the outputs Y₁, Y₂ for all possible inputs A and B
Compare β-particles and γ-rays in terms of their mass, charge, ionizing power and penetrating power.
Define decay constant.
The isotope carbon-14 has half life 5700 years. If the sample contains 10²² carbon-14 nuclei, find its activity.
Group C
Long answer question
In Young’s double slit experiment, bright and dark bands are formed on a screen due to interference of light.
Define interference of light.
Calculate the fringe width (β).
When the whole apparatus is immersed in a liquid, what will be the effect on the fringe width?
A plane transmission grating has 5000 lines per cm and the second order spectral line is diffracted through 30°. Calculate the wavelength of light used.
Bohr’s atomic model is based on quantum theory of radiation.
Write the postulates of Bohr’s atomic model.
Calculate the radius of nth orbit of H-atom using Bohr’s postulates
In an experiment on photoelectric effect, the graph between maximum kinetic energy and frequency of incident radiation on the metal surface is found to be straight line as shown in the figure. Calculate:
Threshold frequency
Planck’s constant.
Work function of metal in eV
A horizontal beam of electrons moving with velocity v passes between two parallel plates as shown in the figure.
Describe the motion of electron and show that the path followed by it is parabolic.
What is cross field? Write one use of cross field.
State Bragg’s law
The largest distance between the interatomic planes of crystal is 10 Å. What is the upper limit for the wavelength of X-rays which can be used to study the crystal?
Define root mean square value of ac.
The given figure shows the LCR series circuit.
Obtain the expression for impedance of the circuit.
What is resonance in LCR series circuit?
Calculate the resonant frequency.
What is quality factor of the circuit?
Lenz law gives the direction of induced emf.
State Lenz law.
Explain how this law is in accordance with the law of conservation of energy.
Obtain a relation for the energy stored in an inductor.
A step down transformer converts a voltage of 2200 Volt into 220 Volt in the transmission line. Number of turns in primary coil is 5000. Efficiency of the transformer is 90% and its output power is 8 kW.
Calculate:
i. Number of turns in the secondary coil
Calculate:
ii. Input power
Paper Overview & Analysis
Set B
Year
Model Question
Type
75
Full Marks
32
Pass Marks
3 Hours
Duration
65
Question Items
Question Type Breakdown
Group Breakdown
Chapter Breakdown
| Interference | 3 items | 6 marks |
| Electromagnetic Induction | 2 items | 4 marks |
| Wave motion | 2 items | 2 marks |
| Rotational Dynamics | 1 item | 1 mark |
| Periodic motion | 1 item | 1 mark |
| Fluid statics | 1 item | 1 mark |
| First law of thermodynamics | 1 item | 1 mark |
| Second law of thermodynamics | 1 item | 1 mark |
| Acoustic phenomena | 1 item | 1 mark |
| Nature and propagation of light | 1 item | 1 mark |
| Electrical Circuits | 1 item | 1 mark |
| Diffraction | 1 item | 2 marks |
Chapter breakdown covers 16 of 65 question items on this paper — the rest aren't tagged to a chapter yet.