LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc. DEGREE EXAMINATION – PHYSICS

XC 50

FIFTH SEMESTER – April 2009

PH 5505 / 4500 – ELECTRICITY & MAGNETISM

 

 

 

Date & Time: 24/04/2009 / 1:00 – 4:00  Dept. No.                                                  Max. : 100 Marks

 

 

PART – A

Answer all questions.All questions carry equal marks.      (10 x 2 = 20marks)

 

1. Define electric dipole moment.
2. Define the capacitance of a capacitor.
3. What is thermo electric power?
4. A reversible cell has an emf of 1 volt at 0 ⁰ C. Assuming that the energy provided by the chemical reactions occurring in the cell amounts to 1.092 J/C, calculate the change in its emf when its temperature rises to 1⁰ C.
5. Define ampere.
6. What is Coefficient of coupling ?
7. If the charge on a capacitor of capacitance is leaking through a high resistance of 100 megaohms is reduced to half its maximum value, calculate the time of leakage.
8. Differentiate series resonant circuit from parallel resonant circuit.
9. Mention any two properties of dia magnetic materials.
10. What is curie temperature ?

 

PART – B

Answer any four questions.                                                         (4×7.5=30marks)

 

11. Obtain expressions for electric potential and electric field at any point due to a dipole.
12. Describe the experimental method of determination of specific conductivity of an

electrolyte using kohlrausch bridge.

13. Derive an expression for the flux density at a point inside a solenoid.
14. a) Write a note on choke coil (4 marks)
15. b) A coil has an inductance of 0.1 H and a resistance of 12 ohms. It is connected

to a 220V, 50Hz mains. Determine the (1) reactance of the coil, (2) impedance

of the coil.                                                                                      (3.5 marks)

15. Using Maxwell’s equations determine the velocity of electromagnetic waves in

free space.

PART – C

Answer any four questions.                                                        (4×12.5=50marks)

 

16. a) Find an expression for the capacity of a cylindrical condenser.               (7.5 marks)
17. b) A co-axial cable consists of a copper core of 1mm radius within an outer metal

sheath of 1cm. radius separated by an insulating material of dielectric constant

5. What is the capacitance per metre length of the cable in pico-farad? (5marks)
6. Define Peltier and Thomson coefficients and derive expressions for them.
7. a) Describe the construction of a moving coil galvanometer and derive an expression

for the quantity of charge flowing through it.                                          (9 marks)

1. b) The successive throws on the same side of the mean position for an oscillating

coil are 25, 24.9 and 24.8 cm. Calculate the logarithmic decrement.       (3.5 marks)

19. Discuss the growth and decay of charge in an LCR circuit.
20. Discuss the Langevin’s theory of paramagnetism.

 

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