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78ET-2
Sr. No. 6
EXAMINATION OF MARINE ENGINEER OFFICER
ELECTRO TECHNOLOGY
CLASS II
(Time allowed - 3 hours)
Total Marks 100
INDIA
N.B. -
Morning Paper
(1) Attempt SIX questions only with minimum of ONE question from each part.
(2) All questions carry equal marks.
(3) Neatness in handwriting and clarity in expression carries weightage
Section A
1. A battery having an E.M.F. of 110 volts and an internal resistance of 0.2 ohm is connected in parallel
with another battery with an E.M.F. of 100 volts and resistance 0.25 ohm. The two batteries in
parallel are placed in series with a regulating resistance of 5 ohms and connected across 200 volt
mains. Calculate the magnitude and direction of the current in each battery and the total current taken
from the supply mains.
2. A D.C. series motor runs at 17 rev/s when taking 20 amperes at 200 volts. The resistance of the
armature winding is 0.5 ohm and that of the field winding 0.2 ohm. Find the speed for a total current
of 20 amperes, 200 volts when a 0.2 ohm resistor is joined in parallel with the field winding. The flux
for a field current of 10 amperes is 70 per cent of that 20 amperes.
3. A choking coil of negligible resistance takes a current of 10 amperes when connected to a 220 volt,
50 Hz supply. A non-inductive resistor under the same conditions takes 12 amperes. If the two are
connected in series and placed across the same supply, find the current taken. If now the frequency is
reduced to 40 Hz, the voltage being maintained constant, find the current taken.
4. A heater is required for an electric boiler and has to run from a 230 V supply. Estimate the resistance
of the heater if it is required to raise the temperature of 3 kg. of water from 100 to 950 C in 16 min. it
may be assumed that the efficiency of the heater is 85 per cent. Find also the necessary length and
cross section of the wire of the heater element to give the result. The resistivity of the material is
50 -cm., and the current density in the wire is 30 A/mm2..
5. A coil of resistance 10  and inductance 0.2 H, in series with a 200  F capacitor, is connected to a
440 V, 50 Hz supply. Calculate (a) The current, (b) The angle of phase difference, (c) The p.f. (d) The voltage across the capacitor.
Give a vector diagram in explanation.
6. A high-voltage, gas-fitted diode has a forward conduction voltage drop of 20V plus 1V for every
ampere conducted. Plot the diode characteristic and hence estimate the power dissipated in the diode
when it is connected in series with a load of resistance 200 to a 5000V supply of polarity such as to
make the diode conduct.
Section B
7. Write notes on the following :(a) Transistors, (b) Capacitors, (c) Inductors,
8. Draw wiring diagram of a fluorescent tube lighting and explain the function of choke, starter,
condenser across starter. What is the purpose of coating inside of the tube with fluorescent powder?
9. Describe and sketch an instrument suitable for measuring the insulation resistance of electrical
equipment. Indicate, by means of sketches, where the terminals of the instrument are connected when
checking the insulation of : (a) Field coil of a generator, (b) Armature of a generator, (c) A section of electric wiring.