Sub. code 1021
NEB — GRADE XII
2080
Old Question
Physics Question Paper 2080 (Old Question)
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 old question question paper is for Class 12 Physics, 2080 (subject code 1021), carrying full marks of 75 with a pass mark of 32, to be completed within 3 Hours. Answers with step-by-step solutions are available for every question below.
Group A
Rewrite the correct options of each questions in your answer sheet.
When the torque acting upon a system is zero which of the following will be constant?
Force
Linear momentum
Angular 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
12P₁V₁
6P₁V₁
3P₁V₁
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 reversibility 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
Short Answer Questions
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 sin ωt,
where r is the amplitude of vibration.
i) Define amplitude.
ii) 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
where symbols have their usual meanings.
i) Define coefficient of viscosity.
ii) 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 with a cross section of 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.
Obtain the efficiency of a heat engine.
The figure shows the variation of thermoemf with the temperature of the hot junction, when the cold junction is at 0°C.
i) What is thermoelectric effect?
ii) Define θₙ and θᵢ.
iii) What will be the effect on θᵢ if we shift the cold junction to −10°C?
iv) Give one of the applications of such thermocouple.
Biot-Savart law gives the magnitude of magnetic field produced by a current carrying conductor.
i) State Biot-Savart law.
ii) Use Biot-Savart law to calculate the magnetic field of a circular current carrying coil at its centre.
iii) 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.
i) Define harmonics and overtone.
ii) Calculate the frequency of this mode.
iii) If the tension of the string is increased 4 times, what will be the frequency of this mode?
i) Write down Newton's formula for the velocity of sound in a gas medium with its discrepancy.
ii) Obtain Laplace's corrected formula.
iii) 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.
i) Describe the formation of potential barrier.
ii) 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 at 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 Questions
In Young's double slit experiment, bright and dark bands are formed on a screen due to interference of light.
i) Define interference of light.
ii) Calculate the fringe width (β).
iii) 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.
i) Write the postulates of Bohr's atomic model.
ii) 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:
i) Threshold frequency.
ii) Planck's constant.
iii) 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.
i) Describe the motion of electron and show that the path followed by it is parabolic.
ii) What is cross field? Write one use of cross field.
i) State Bragg's law.
ii) The largest distance between the inter atomic 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.
i) Obtain the expression for impedance of the circuit.
ii) What is resonance in LCR series circuit?
iii) Calculate the resonant frequency.
iv) What is quality factor of the circuit?
Lenz law gives the direction of induced emf.
i) State Lenz law.
ii) 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 the 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.
ii) Input power.