CBSE Sample Papers for Class 12 Physics Solved 2016 Set 11

# CBSE Sample Papers for Class 12 Physics Solved 2016 Set 11

## CBSE Sample Papers for Class 12 SA2 Physics Solved 2016 Set 11

### Section A

1.Calculate the speed of light in a medium whose critical angle is 30°.

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2.Two identical loops, one of copper and the other of aluminium, are rotated with

the same angular speed in the same magnetic field. Compare the induced emf in two coil loops.

3.Name the part of electromagnetic spectrum of wavelength 10 2 m and mention its one application.

4.The I-V characteristic of a resistor are observed to deviate from a straight line for

higher values of current as shown alongside. Why?

5.State the relation the frequency v of radiation, emitted by a LED and the band gap energy E of the semiconductor used to fabricate it.

### Section B

6.Draw the waveforms for the input AM wave at A and output signal B, of the envelope detector

7.An electric dipole of dipole moment p is placed in a uniform electric field Write the expression for the torque x experienced by the dipole. Show diagrammatically the orientation of the dipole in the field for which the torque is half of the maximum value. (2)

Or

In what ways, does a charge differ from mass?

8.In an electromagnetic wave propagating along the X-direction, the magnetic field oscillates at a frequency of 3 x 10[1] Hz and has an amplitude of 10 ~7 T, acting along

the Y-direction.

• What is the wavelength of the wave?
• Write the expression representing the corresponding oscillating electric field.

An AC generator consist of coil of 100 turns and cross-sectional area of 3 m2, rotating at a constant angular speed of 60 rad s-1 in a uniform magnetic field 0.04 T. The resistance of the coil is 500 Q. Calculate

• maximum current drawn from the generator and
• minimum power dissipation of the coil.

9.(i) A plane wavefront approaches a plane surface separating two media. If medium

‘one’ is optically denser and medium ‘two’ is optically rarer, using Huygen’s principle, explain and show how a refracted wavefront is constructed?

(ii) When a light wave travels from a rarer to a denser medium, the speed decreases. Does it imply reduction in its energy? Explain

10. An AC generator consist of coil of 100 turns and cross-sectional area of 3 m2, rotating at a constant angular speed of 60 rad s-1 in a uniform magnetic field 0.04 T. The resistance of the coil is 500 Q. Calculate

• maximum current drawn from the generator and
• minimum power dissipation of the coil.

### Section C

11.Figure shows two identical capacitors Cx and C2, each of 2pF capacitance,

connected to a battery of 5 V Initially switch S is closed. After sometime, S is left open and dielectric slabs of dielectric constant K = 5 are used inserted to fill completely the space between the plates of the two capacitors. How will the charge and (ii) potential difference between the plates of the capacitors be affected after the slabs are inserted?

12. (i) What happens when a diamagnetic substance is placed in a varying magnetic field?

(ii) Name the properties of a magnetic material that make it suitable for making

• a permanent magnet and
• a core of an electromagnet.

13. Four identical cells, each of emf 8 V and internal resistance 2.5 Q are connected in series and charged by a 100 V DC supply, using a 24 Q resistor in series. Calculate the following

• charging current in the circuit
• potential difference across the cells during recharging.

14. A ray of light falls on a transparent right angled isosceles prism made from a glass of

refractive index root 2. Draw a ray diagram for this prism when the light ray falls normally on one of the equal sides of the prism.

15. (i) In a Young’s double slit experiment, the two slits are kept 2 mm apart and the screen

is positioned 140 cm away from the plane of the slits. The slits are illuminated with light of wavelength 600 nm. Find the distance of the third bright fringe, from the central maximum, in the interference pattern obtained on the screen.

(ii) If the wavelength of the incident light were changed to 480 nm, then find out the shift in the position of third bright fringe from the central maximum. (3)

Or

• What are coherent sources of light? Why are coherent sources required to obtain sustained interference pattern?
• State three characteristic features which distinguish the interference pattern due to two coherently illuminated sources as compared to that observed in a diffraction pattern due to a single slit.

17. Deduce an expression for the electric potential due to an electric dipole at any point

on its axis. Mention one contrasting feature of electric potential of a dipole at a point as compared to that of due to a single charge.

19. (i) What is amplitude modulation?

(ii) Define modulation index,

(iii) Show amplitude modulation graphically.

20. Draw transfer characteristics of a common emitter n-p-n Point out the region in which the transistor operates as an amplifier. Define the following terms used in transistor amplifiers.

(i) Input resistance (ii) Output resistance (iii) Current amplification factor

21. (i) Using de-Broglie’s hypothesis, explain with the help of a suitable diagram, Bohr’s

second postulate of quantisation of energy levels in a hydrogen atom.

(ii) The ground state energy of hydrogen atom is -13.6 eV What are the kinetic and

potential energies of the electron in this state?

### Section D

23. Ramesh and his younger brother Raju went to a shopping mall whose doors were automatic with self close and open. Raju asked Ramesh, that, “Why these doors are automatically open and closing without even a single touch?”. Ramesh was a graduate, but he did not know the exact reason behind this. Ramesh asked the same from his friend Rakesh who was junior to him Rakesh explained the whole phenomenon agilely to Ramesh and told that this whole phenomenon is based on photoelectric effect given by the great scientist Einstein.

• State the laws of photoelectric effect.
• Write photoelectric equation given by Einstein and define photoelectric current.

### Section E

24. (i) Derive an expression for the force between two long parallel current carrying conductors.

• Use this expression to define SI unit of current.
• A long straight wire AB carries a current A proton P travels with a speed v, parallel to the wire, at a distance d from it, in a direction opposite to the current as shown in the figure. What is the force experienced by the proton and what is its direction?

or

A straight horizontal conducting rod of length 0.45 m and mass 60 g is suspended by two vertical wires at its ends. A current of 5.0 A is set up in the rod through the wires.

• What magnetic field should be set up normal to the conductor in order that the tension in the wires is zero?
• What will be the total tension in the wires, if the direction of current is reversed keeping the magnetic field same as before? (Ignore the mass of the wires) (g =9.8 ms-2).

25. What is induced emf? Write Faraday’s law of electromagnetic induction. Express it mathematically.

A conducting rod of length 1, with one end pivoted is rotated with angular speed in a vertical plane, normal to a uniform magnetic field B. Deduce an expression for the emf induced in this rod.

If resistance of rod is R, then what is current induced in it?

or

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