Sub. code 1021
NEB — GRADE XII
2081
Old Question
Physics Question Paper 2081 (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, 2081 (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
Multiple Choice Questions
If the rotational kinetic energy of a body is E and moment of inertia is I, then angular momentum will be:
EI
√2EI
E/I
√IE
The displacement versus time graph of particles in SHM is shown in figure. The maximum velocity of the particle is:
1 cm s⁻¹
0.2 cm s⁻¹
3.14 cm s⁻¹
31.4 cm s⁻¹
Two capillary tubes P and Q of radii 4 mm and 2 mm are dipped in water. What is the ratio of heights through which liquid rises in the tubes P and Q?
1:2
2:1
1:4
4:1
A system undergoes an isochoric process so that its temperature changes from 127°C to 227°C. What is the ratio of initial pressure to final pressure?
4/5
5/4
227/127
127/227
Given figure represents the block diagram of a heat engine. What is the efficiency of this engine?
25%
50%
60%
75%
What is the distance between two consecutive particles in a wave which are in the same phase?
λ/4
λ/2
3λ/4
λ
A polarizer is used to
reduce intensity of light
produce diffracted light
increase intensity of light
produce unpolarized light
Which of the following is the ferromagnetic material?
Aluminium
Gold
Copper
Cobalt
The temperature of inversion of a thermocouple is 600°C and the neutral temperature is 310°C. What must be the temperature of cold junction?
0°C
10°C
20°C
30°C
In our country Nepal, the supply ac voltage is 220 V. The peak value of voltage is about
110 V
220 V
310 V
350 V
If a P-wave were to go from a solid to a liquid, what would happen to its velocity?
Remains the same
Increases
Decreases
Decreases up to zero
Group B
Short Answer Questions
Define the moment of inertia.
A uniform rod of mass m and length L is rotating about an axis AB passing through its one end and perpendicular to the length. Calculate the moment of inertia of the rod about the axis AB.
A fly wheel of moment of inertia 0.32 kgm² is rotated steadily at 120 rad/sec by a 50 watt electric motor. Calculate:
i) The kinetic energy of the fly wheel.
ii) The frictional couple opposing the rotation.
One end of a light spring having spring constant 18 N/m is attached to a rigid support. A mass of 0.15 kg is suspended from other end of the spring. A student pulls down it such that extension of spring increases by 4 cm. The student now releases it, as a result, the mass performs SHM.
i) Define simple harmonic motion. [1]
ii) Calculate the maximum acceleration and time period of SHM. [2]
Write an expression for total energy of a particle executing SHM. Also draw a graph showing the variation of K.E. and P.E. of it
Derive a relation between surface tension and surface energy.
N identical spherical drops of water falling with a terminal velocity v₁ coalesce to form a bigger drop and fall with a new terminal velocity v₂ through air. (Neglect air resistance.)
i) Obtain a relation between v₂ and v₁. [2]
ii) If N = 2 and v₁ = 0.4 m s⁻¹, then calculate v₂. [1]
The given figure represents the P-V diagram of a cyclic process.
Define indicator diagram.
Estimate the work done during II process.
Identify the thermodynamic processes represented by I, II, III and IV.
What correction is made by Laplace over the Newton's formula for velocity of sound in a gas? Obtain the corrected formula.
Calculate the wavelength of wave in air at 25°C if the frequency of the wave is 256 Hz and velocity of sound at 0°C is 330 m s⁻¹
The arrangement of potentiometer circuit for the determination of internal resistance of a cell (r) is shown in figure. Derive an expression for internal resistance of the cell.
How can you convert a galvanometer into an ammeter of suitable range?
Obtain an expression for the magnetic field intensity at any point due to a straight current carrying conductor using Ampere's circuital law.
A wire of length 0.5 m carrying a current of 2 A is placed in a uniform magnetic field of strength 0.4 T. Find the maximum and minimum force experienced by it.
Explain quantization of charge.
An ion of specific charge 4.40 × 10⁷ C/kg is moving in a circular orbit in a magnetic field of flux density 0.4 T with velocity of 3.52 × 10⁵ m s⁻¹. Calculate the radius of this orbit.
Why are X-rays used in Millikan's oil drop experiment?
Define the terms half life and mean life of a radioactive substance.
If 2 gm of a radioactive material having half life period of 50 years disintegrates, find out mean life of the given sample.
Given figure represents decay graph of a radioactive sample of half life 10 years. Estimate the value of T₃.
What is rectification? Explain full wave rectification using two P-N junction diodes.
For the digital circuit given below write the truth table showing the outputs A′, B′ and Y for all possible inputs A and B.
Group C
Long Answer Question
The diagram shows a standing wave in an open organ pipe.
i) Redraw the diagram and show the position of nodes and antinodes.
ii) Derive an expression for frequency of this mode.
What will be the effect of velocity of transverse wave in a stretched string if the radius of the string is doubled?
A car is sounding its horn and has a frequency 400 Hz and travelling towards a stationary traffic post. A traffic police at the post detects the change in frequency of 60 Hz when the car crosses him. Find the velocity of the car.
(Velocity of sound in air is 340 m s⁻¹)
How can a plane wavefront be converted into a spherical wavefront? Justify
What is interference of light? Two coherent waves, each of intensity I, are producing an interference pattern. What will be the resultant intensity at a point of:
i) Constructive interference
ii) Destructive interference
A monochromatic light of wavelength 5890 Å is incident normally on a diffraction grating which has 6000 lines per centimeter.
i) At what angle will the second order image be seen?
ii) Is third order image possible with this grating?
A moving coil is very sensitive device to measure very small current.
i) Define voltage sensitivity of moving coil galvanometer. On which factors does it depend?
ii) Why is magnetic field made radial in a moving coil galvanometer?
State Faraday's laws of electromagnetic induction. The magnetic flux passing perpendicular to the plane of a coil is given by
where φ is in weber and t is in seconds. Calculate the magnitude of instantaneous emf induced in the coil when t = 3 s.
Derive an expression for energy stored in an inductor.
Obtain an expression for magnetic field strength at the centre of current carrying circular coil using Biot-Savart's law.
A slice of indium antimonide 2.5 mm thick carries a current of 150 mA. A magnetic field of flux density 0.5 T, correctly applied, produces a maximum Hall voltage of 8.75 mV between the edges of the slice. Calculate the number of free charge carriers per unit volume assuming they each have a charge of −1.6 × 10⁻¹⁹ C.
Derive an expression for the force exerted per unit length between two parallel current carrying conductors if currents are flowing in the same direction. Hence, define one ampere current.
Explain photoelectric effect and write Einstein photoelectric equation.
Obtain an expression for the velocity of an electron in the first excited state.
Calculate the de-Broglie wavelength of an electron which has been accelerated through a potential difference of 300 V.
(Mass of electron = 9.1 × 10⁻³¹ kg, Planck's constant, h = 6.6 × 10⁻³⁴ Js)