## CBSE Sample Papers for Class 12 Physics Solved 2016 Set 13

Section A

1.What is the speed of electromagnetic wave in a medium?

2.Define the term “stopping potential” in relation to photoelectric effect.

3.A proton has spin and magnetic moment just like an electron. Why then its effect  is neglected in magnetism of materials?

4.What is the magnetic moment associated with a coil of a turn, area of cross-section 10~4 m2 and carrying current of 2 A?

5.  A wire of resistance 16 R is bent in the form of a circle. What is the effective resistance between the ends of a diameter AB ?

### Section B

6. State four properties of electromagnetic wave?

7.Draw the logic circuit for combination of gates in figure and also write truth table for same 8.A large circular coil of radius R and a small circular coil radius r are put in vicinity of

each other. If the coefficient of mutual induction for this pair, equals 1 mH, what would be the flux linked with the larger coil when a current of 0.5 A flows through the smaller coil? When the current in the smaller coil falls to zero, what would be its effect in the larger coil?

Or

Current in a circuit falls steadily from 2.0 A to 0.0 A in 10 ms. If an average emf of 200 V is induced, calculate the self-inductance of the circuit.

9.Name any two types of transmission media that are commonly used for transmission of signals.  Write the range of frequencies of signals for which these transmission media are used.

10. Differentiate between a ray and a wavefront. Draw a diagram to show refraction of a plane wavefront incident in a convex lens and hence draw the refracted wavefront

### Section C 12. Draw the circuit diagram of a potentiometer which can be used to determine the  internal resistance r of a given cell of emf E. Explain briefly how the internal resistance of the cell is determined?

13. A coil of 0.01 H inductance and 1 ohms resistance is connected to 200 V, 50 Hz AC  supply. Find the impedance of the circuit and time lag between maximum alternating voltage and current.  16  (i) Use the mirror equation to show that a convex mirror always produces a virtual

image independent of the location of the object.  An object placed between the pole and focus of a concave mirror produces a virtual and enlarged image.

(ii) Use the lens equation deduce algebraically that an object placed with in the focus of a convex lens produces a virtual and enlarged image.    21. A long straight wire of a circular cross-section of radius a, carries a steady current I. The current is uniformly distributed across the cross-section of the wire. Use Ampere’s circuital law to show that the magnetic field, due to this wire, in the region inside the wire, increases in direct proportional to the distance of the field point from the axis of the wire. Write the value of this magnetic field on the surface of the wire.

22.  Define the term work function of a metal. The threshold frequency of a metal is f 0.

When the light of frequency 2f0 is incident on the metal plate, the maximum velocity of electrons emitted is v1. When the frequency of the incident radiation is increased to 5 f0, the maximum velocity of electrons emitted is v2 • Find ratio of v1 to v2.

### Section D

23. Once upon a time, a school organised science fair. Students of class XII bring mirrors in their classroom. The mirrors are so arranged that one can see five images of himself. All the students of other classes who came to see this were very happy and Neha a class Xth student was determined to know the reason behind it. She went to the library, consulted other students and next day came up with the answer.

• What values were dedicated by Neha?
• Explain the formation of odd number of images.
• Give the reason for five images

### Section E

24. (i) Using the necessary circuit diagram, draw the transfer characteristics of a base-biased transistor in CE configuration. With the help of these characteristics, explain briefly how the transistor can be used as an amplifier.

(ii) Why are NAND gate called universal gates?  Identify the logic operations carried out by the circuit Shown alongside. Or

• Draw a circuit diagram to study the input and output characteristics of an n-p-n transistor in its common emitter configuration. Draw the typical input and output characteristics.
• Explain, with the help of a circuit diagram,  the working of n-p-n transistor as a common emitter amplifier.  or

• In what way is diffraction from each slit related to the interference pattern in a double slit experiment?
• Two students are separated by a 7 m partition wall in a room 10 m high. If both light and sound waves can bend around obstacles, how is it that the students are unable to see each other even though they can converse easily?
• When a low flying aircraft passes overhead, we sometimes notice a slight shaking of the picture on our TV screen. Suggest a possible explanation.  