# AHSEC - Class 12 Question Papers: Physics' 2015

2015
PHYSICS (Theory)
Full Marks: 70

Time: 3 hours
The figures in the margin indicate full marks for the questions

1. Answer the following questions: 1x8=8
1. What is quantization of charge?
2. Why is the Cyclotron not used to accelerate electrons?
3. If R and L represent resistance and inductance respectively then what is the dimension of L/R.
4. Out of the four Maxwell’s equations, which equation establishes the non-existence of magnetic monopole?
5. What is the shape of the wave front of light emitted by a long neon bulb placed at a finite distance?
6. Give the dimension of Planck’s constant.
7. What is an ?
8. What is reversed Saturation Current?
2. Calculate the magnitude of electrostatic force between a proton and an electron separated by a distance . Given that magnitude of charge of proton and electron to be each and 2
Or
A. 100pF capacitor is charged by a potential difference of 100V. What is the amount of charge stored? What is the electrostatic energy stored in the capacitor? 2
3. An-identical cells each of e.m.f E and internal resistance r are connected in series. Find the expression for current in the circuit given below. Or
Establish the following relation for drift velocity. 2 where symbols have their usual meaning.
4. A copper wire is stretched so as to increase its length by 0.2%. Calculate the percentage change in the resistance of the wire. 2
Or
A 100W heater coil is rated 200V. Find the resistance of the coil. 2
5. Show that total energy required to build up a current I in an inductor of coefficient of induction L is 2
Or
Find the expression for mutual inductance between a pair of co-axial coils. 2
6. A metal rod of length L meter rotates about one end in a vertical plane at right angles to the magnetic meridian. Frequency of revolution is f HZ. If the Horizontal component of Earth’s magnetic field is H Tesla then find the expression of induced emf between the ends of the rod. 2
Or
Find the peak current in the circuit given below: 2 7. What is power factor of an L-C-R circuit? Explain on the basis of power factor that an ideal inductor is a Wattless component. 2
Or
Why is electrical energy transmitted at high voltage from a distant power generating station? 2
8. Write down the expression for the velocity of electromagnetic wave in a medium and hence find out an expression for the refractive index of the medium. 2
Or
9. Draw a ray diagram to show the formation of final image at least distance of distinct vision by a compound microscope. 2
Or
Draw a ray diagram for the formation of an image by a reflecting telescope.
10. Obtain Bohr’s quantization condition on the basis of the wave nature of an electron. 2
Or
Describe in brief the process of gamma radiation. 2
11. What percentage of power of AM wave is carried by the side bands for modulation index m = 1? 2
Or
How is the critical frequency related to electron density in the ionosphere? 2
12. Draw the circuit diagram of a potentiometer to compare the emf of two cells and briefly describe the procedure. 3
Or
Draw the circuit diagram of a potentiometer to determine the internal resistance of a cell and briefly describe the procedure. 3
13. A coil of area A, number of turns N and resistance R is rotating in a radial magnetic field B with an angular speed w. What is the maximum power consumed by the coil? 3
Or
An AC source of is connected across in inductor having resistance and self inductance 2H. Calculate – 3
1. Frequency of AC.
2. Total impedance of the circuit.
3. Peak value of the current flowing through the circuit.
14. Derive the expression for the equivalent focal length of a combination of two thin convex lenses in contact.       3
Or
Deduct the relation for a convex lens producing virtual image. 3
15. Establish Brewster’s Law of polarization of light. 3
Or
What is a Coherent Source? State two difference between interference and diffraction. 3
16. A monochromatic source of light operating at 200W emits photons/sec. Find the wavelength of the light. Given 3
Or
What is the de-Broglie wavelength of an electron in the Bohr’s orbit of radius in hydrogen atom?    3
17. Derive an expression for the radius of the first orbit of the electron of the hydrogen atom. 3
Or
Obtain the binding energies of the nuclei and in units of from the given data Which nucleus has greater binding energy per nucleon? 3
18. How is a NOT gate realised with the help of a transistor? Give its truth table. 3
Or Of transistor are 120. What is the change in collector current for change in base current? Draw at least two input characteristics of a CE mode transistor. 3
19. What is breakdown voltage of a Zener diode?  Explain its use as a voltage regulator. 3
Or
Draw a circuit diagram of a full wave rectifier and explain its working. 3
20. What is digital communication? Mention two advantages of digital communication. 3
Or
What are sidebands of an AM wave? Compare AM and FM wave. 3
21. Define electric dipole and dipole moment. Derive an expression for electric field intensity at a point on the axial line of an electric dipole. 5
Or

Explain the concept of electric field. Express electric flux through a surface in terms of electric field intensity. Show that the electric flux through a cylindrical surface with its axis parallel to a uniform electric field is zero. 5