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Q5. With reference to a three-phase shipboard electrical distribution system: A. Enumerate the advantages of an insulated neutral system; B. Enumerate the disadvantages of an insulated neutral system; C. Describe how the earthed neutral system is Earthed; D. Compare the use of an insulated neutral system as opposed to the use of an Earthed Neutral System with regard to the risk of electric shock from either system.

Q2. A. i.  Describe the characteristics of a d.c. motor. ii Explain the advantages of such a motor for deck machinery; B. Describe with the aid of a sketch a control system for the motor in (A).

Q4. List at least two factors that cause deterioration of the frequency response of a transistor amplifier. Explain how each factor affects the performance of the amplifier and the portion of the frequency range where it is effective.

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

A. Rectifier circuit;

B. Amplifier circuit;

C. Oscillator circuit.

Q3. A) Describe the circuit breaker for an a.c. generator using a sketch to show how arcing is Controlled.

(B)Explain the sequence of events that might occur if the breaker opens on a short circuit and state the check you would require following such event;

(C) Give a safe procedure to follow should a main circuit breaker fail to open under fault Condition.

Q6. What design factor limits the maximum torque of a d-c motor? Of an a-c motor? A shunt motor runs on no load at 700 r/min off a 440 V supply. The resistance of the shunt circuit is 240?. The following table gives the relationship between the flux and the shunt current: Calculate the additional resistance required in the shunt circuit to raise the no-load speed to 1000 r/min.

Shunt current (A)
0.5
0.75
1.0
1.25
1.5
1.75
2.0
Flux per pole (m Wb)
6.0
8.0
9.4
10.2
10.8
11.2
11.5

Q7. A. On what factors does the capacitance of a parallel-plate capacitor depend? B. A tuned circuit consisting of a coil having an inductance of 200µ H and a resistance of 20Ω in parallel with a variable capacitor is connected in series with a resistor of 8000Ω across a 60 V supply having a frequency of 1 MHz. calculate A. The value of C to give resonance; B. The dynamic impedance and the Q factor of the tuned circuit; C. The current in each branch

Q8. A. What is reactive power? Why is such term not encountered when d-c sources are used in electric circuit? B. A transistor amplifier stage comprises a transistor of parameters hie = 800 Ω and hfe = 50 and hoe = 20µ S, and bias components and coupling capacitors of negligible effect. The input signal consists of an e.m.f of 60mV from a source of internal resistance 2.2k Ω and total load on the stage output is 4k Ω. Determine the current, voltage and power gains of the amplifier stage.

Q6. (a). Explain the significance of the root- mean- square value of an alternating current or voltage waveform; Define the form factor of such a wave form.

(b). A total load of 8000 kW at 0.8 power factor is supplied by two alternators in parallel. One alternator supplies 6000 kW at 0.9 power factor. Find the kVA rating of the other alternator and the power factor.

Q7. A. By means of a schematic circuit diagram illustrate the peak rectifier. If the supply voltage is v(t) = Vm Sin wt, what is the voltage across the load resistor?

B. A battery-charging circuit is shown below in Fig. The forward resistance of the diode can be considered negligible and the reverse resistance infinite. The internal resistance of the battery is negligible. Calculate the necessary value of the variable resistance R so that the battery charging current is 1.0 A.