" /> -->

#### Full Portion Three Marks Question

12th Standard EM

Reg.No. :
•
•
•
•
•
•

Physics

Time : 01:30:00 Hrs
Total Marks : 60
20 x 3 = 60
1. Consider two point charges q1 and q2 at rest as shown in the figure.

They are separated by a distance of 1m. Calculate the force experienced by the two charges for the following cases:
(a) q1 = +2μC and q2 = +3μC
(b) q1 = +2μC and q2 = -3μC
(c) q1= +2μC and q2 = -3μC kept in water (εr = 80)

2. Consider four equal charges q1,q2, q3 and q4 = q = +1μC located at four different points on a circle of radius 1m, as shown in the figure. Calculate the total force acting on the charge q1 due to all the other charges.

3. (a) Calculate the electric potential at points P and Q as shown in the figure below.
(b) Suppose the charge +9μC is replaced by -9μC find the electrostatic potentials at points P and Q.

(c) Calculate the work done to bring a test charge +2μC from infinity to the point P. Assume the charge +9μC is held fixed at origin and +2μC is brought from infinity to P.

4. Define potential difference and derive.

5. Consider a rectangular block of metal of height A, width B and length C as shown in the figure.

If a potential difference of V is applied between the two faces A and B of the block (figure (a)), the current IAB is observed. Find the current that flows if the same potential difference V is applied between the two faces B and C of the block (figure (b)). Give your answers in terms of IAB.

6. Calculate the magnetic field at a point on the axial line of a bar magnet.

7. What is the value of magnetic field at point O due to current flowing in the wires?

8. The magnetic flux passes perpendicular to the plane of the circuit and is directed into the paper. If the magnetic flux varies with respect to time as per the following relation: $\Phi_B$=(2t3+3t2+8t+5)mWb, what is the magnitude of the induced emf in the loop when t = 3 s? Find out the direction of current through the circuit.

9. What is impedance? When does LCR circuit have minimum impedance?

10. Obtain the equation for lateral displacement of light passing through a glass slab

11. A thin rod of length f /3 is placed along the optical axis of a concave mirror of focal length f such that its image which is real and elongated just touches the rod. Calculate the longitudinal magnification.

12. Determine the focal length of the lens made up of a material of refractive index 1.52 as shown in the diagram. (Points C1 and C2 are the centers of curvature of the first and second surface.)

13. If the focal length is 150 cm for a glass lens, what is the power of the lens?

14. (i) Draw a graph showing variation of photoelectric current (I) with anode potential (V) for different intensities of incident radiation. Name the characteristic of the incident radiation that is kept constant in this experiment.
(ii) If the potential difference used to accelerate electrons is doubled, by what factor does the de-Broglie wavelength associated with the electrons change?

15. Discuss the Millikan's oil drop experiment to determine the charge of an electron.

16. In a transistor connected in the common base configuration, α = 0.95, IB = mA. Calculate the values of IC and IB

17. Give the Schematic representation of valence band, conduction band, and forbidden energy gap. and draw energy band structure of
(a) Insulators
(b) Semiconductors
(c) Metals?

18. A transmitting antenna has a height of 40 m and the height of the receiving antenna is 30 m. What is the maximum distance between them for line-of-sight communication? The radius of the earth is 6.4×106 m.

19. Write the advantages of AM.

20. What is robotics?