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Q1. Differentiate with the aid of simple sketches between the following types of Electronic circuits.

i) Rectifier circuit

ii) Amplifier circuit

iii) Oscillator circuit

Q2.a) Sketch a circuit for a basic d.c. voltage stabilisation circuit using a Zener diode and a series resistor.

b) Sketch & describe the reverse current characteristic for a typical Zener diode.

c) List the factors which determine the value of the series resistor in the circuit.

d) List the factors that determine the power rating of the chosen Zener diode.

Q3. Discuss magnetic leakage in a Transformer, and indicate how its value may be kept down, show, by means of a vector diagram, how the voltage regulation of a transformer is influenced by its magnetic leakage.

Q4. a) Describe the possible causes and the effect of running a three-phase motor with one phase open circuit. (6)

b) A heater unit of inductance has a resistance of 6.5 ohms and is intended for use with 100V mains. For 50Hz what voltage would it be suitable when placed in series with an external apparatus, of negligible resistance, having an inductance of 0.01H? If the frequency rises by 5 percent and this voltage remains constant, what would be the resulting change of voltage at the heater terminals? (10)

Q5. a) Explain the applications of PN junction diode (6)

b) In a full wave rectifier without filter, the load resistance is 4 k Ω. Each diode has a forward resistance of 0.8 k Ω. If the peak voltage applied to each diode is 120 V at 50Hz, calculate:

(i) The average value of current.

(ii) Efficiency and

(iii) Regulation at a load current of 10mA (10)

Q6.a) Derive an expression for the emf induced in an a.c. generator. (6)

b) A 3000 KVA, 6-pole alternator runs at 1000 r.p.m. in parallel with other machines on 3300V bus-bars. The synchronous reactance is 25%. Calculate the synchronizing power for one mechanical degree of displacement and the corresponding synchronizing torque. (10)

Q7. With reference to oil monitoring of bilge and tanker ballast discharges:
a) Describe with the aid of a sketch, the general arrangement of an oil monitoring system. (8)
b) State the inputs that are recorded. (4)
c) Explain the difficulties encountered with the efficient operation of the oil monitoring system. (4)

Q9. With reference to an automatic water sprinkler, fire detecting alarm and extinguishing system for accommodation spaces:

a) Sketch a typical system. (4)

b) Describe the operation of this system. (4)

c) State the sources of water available. (2)

d) Describe the sprinkler head and its operation. (3)

e) State how the temperature rating of the sprinkler head is determined. (3)

Q9.a) Draw and Explain flammability diagram (4)

b) What is critical dilution in flammability diagram?  (4)

c) How does inert gas reduce flammability range.

d) Describe purging and gas freeing operation of cargo tank in Crude Oil Tanker. (4)