Annamalai University 2010-1st Year B.Sc Electronics Equipment Maintenance - - Electronic Science - - I - Electricity and magnetism - Question Paper

B.Sc. DEGREE EXAMINATION, 2010
( ELECTRONIC SCIENCE )
( 1st YEAR )
( PART - III )
( GROUP - A - MAIN )
( PAPER - I )
530. ELECTRICITY AND MAGNETISM
May ] [ Time : three Hours
Maximum : 100 Marks
PART - A (5 × four = 20)
ans any 5 ques..
All ques. carry equal marks.
1. find an expression for the intensity due to an infinite cylinder.
2. Derive an expression for the force ranging from 2 current carrying long parallel conductors.
3. define the domain theory of ferromagnetism.
4. describe susceptibility and permeability. Show that ? m = ( µr - one ).
5. discuss co-efficient of coupling ranging from 2 coils.
6. find an expression for the self induction of a solenoid.
7. A circuit contains an inductance and a resistance. If it is subjected to an alternating
emf, determine the current in the circuit.
8. find an expression for the growth of charge in a capacitor through a resistance.
PART - B ( five × 16 = 80)
ans any 5 ques..
All ques. carry equal marks.
9. (a) Derive an expression for the potential at
(i) An external point.
(ii) An internal point.
(iii) A point on the surface due to a uniformly charged spherical conductor.
(b) 2 charges +q and -3q are separated by a distance of one m. At what points on its axis is the potential zero ?
10. (a) What is the principle of a capacitor ?
(b) Derive an expression for the capacity of a parallel plate capacitor.
(c) A parallel plate capacitor of capacity 500 pf is to be constructed using paper sheets of thickness of 0·04 mm as dielectric. obtain how many sheets of rectangular metal foils of area 300 sq.cm
are to be used. The dielectric constant for paper is 4.
11. (a) discuss the principle of a potentiometer.
(b) discuss how you could use it to determine the internal resistance of a cell.
(c) In an experiment with a potentiometer to measure the internal resistance of a cell,
when the secondary circuit is shunted by five O , the null point is at 2·20 m. When
the cell is shunted by 20O , the null point is 3·00 m. compute the internal resistance
of the cell.
12. discuss Langevin 's theory of paramagnetism.
13. (a) provide the theory of a moving coil Ballistic galvanometer.
(b) How is the damping correction made ?
(c) The resistance of the coil of a BG is 125O. A steady p.d of three × 10-4 volt provide
a deflection of 16 cm. The system has a period of 10 seconds. When a capacitor
is discharged through the galvanometer, the throw is five cm. obtain the volume of
electricity passed through the galvanometer.
14. define Anderson 's bridge method for the determination of co-efficient of self inductance
of a coil.
15. (a) discuss the principle and working of a transformer.
(b) explain the loss of energy in a transformer.
(c) compute the current which flows in a resistance of 5O connected to a secondary coil of 60 turns, if the primary has 12,000 turns and is connected to 240 V AC supply, assuming that there
are no losses.
16. (a) A circuit is made up of a source of constant emf, a self inductance, an ohmic
resistance, a capacitor and a key in series. Assuming the capacitor is
uncharged before closing the key, investigate theoretically, how its charge
varies with time after closing the key.
(b) A battery of emf 100 volt is connected in series with an inductance of 10mH, a
capacitor of 0·05 µf and a resistance of 100 O . Is the circuit oscillatory ? If so,
what is the frequency of oscillation ?

Earning:   Approval pending.