DieselShip's Online Content Library

Q6.a) Explain the applications of PN junction diode. (6)

b) A full-wave, 1 -phase rectifier employs a double diode valve, the internal resistance of each element of which may be assumed constant at 500 W. The transformer r.m.s. secondary voltage from the centre-tap to each anode is 300 V and the load has a resistance of 2000 W.  Evaluate:-   (10)

(i) mean load current.

(ii) r.m.s. value of load current

(iii) the d.c. output power

(iv) the input power to the anode circuit

(v) the rectification efficiency

Q10. (A) Compare the effectiveness of a current limiting circuit breaker with that of a HRC fuse. (6)

(B) Evaluate for a frequency of 15 kHz, the amplification and the phase difference between input and output signals of a voltage amplifier using a triode having an amplification factor of 48 and a mutual conductance of 1.2 mA/V with an anode-load resistant of 160 k𝛀. The output p.d. is fed by a coupling capacitor of negligible reactance to a subsequent circuit of resistance 480 k𝛀 and the total shunt capacitance is 90 µF. (10)

Q8. a) What is Prismatic Co-efficient (CP). Derive the formula CP =

, where

= Co-efficient of fineness and

= midship section area co-efficient. (6)
b) A watertight door is 1.2m high and 0.75m wide, with a 0.6m sill. The bulkhead is flooded with seawater to a depth of 3m on one side and 1.5m on the other side. Draw the load diagram and from it determine the resultant load and position of the centre of pressure on the door. (10)

Q6. (a) What is the purpose of conducting an inclining experiment on a new vessel? (6)

(b) When a mass of 6t is moved transversely through a certain distance on a ship of 4300t displacement, the deflection of an 11m pendulum is found to be 120 mm. The transverse meta-centre is 7.25 m above the keel and KG 5.46 m. Find the distance through which 6t was moved. (10)

Q6. The ratios of length, breadth and draught of a vessel are 18.5: 2.5: 1. The water plane area coefficient is 0.73 and the TPC is 0.77 more in sea water than in fresh water. Calculate the beam of the ship and TPC in fresh water. (16)

Q6. a) Explain, with reference to moments about the Centerline, how the list may be removed. (6)

b) A ship of 12,250 tonnes displacement, has KM=8 metres, KB=3.8 metres, KG=8 metres and is floating upright. Find the list if a weight of 2 tonnes, already on board, is shifted transversely through a horizontal distance of 12 metres assuming that the ship is wall-sided (10)

Q8. a) Describe in detail the method used to measure the capacitance of a capacitor.(6)

b) A circuit has a resistance of 3R and an inductance of 0.01 H. The voltage across its ends is 60V and the frequency is 50Hz. Calculate (a) the impedance. (b) the power factor (c) the power absorbed.(10)

Q7. In the following circuit, E1 = 13 V, E2 = 19.5 V, R1 = 5 W, R2 = 7 W, R3 = 9 W. Find the current flowing through each resistor. (16)

Q7. An amplifier has an open-circuit voltage gain of 1000, an input resistance of 2000 Ω and an output resistance of 1.0 Ω. Determine the input signal voltage required to produce an output signal current of 0.5A in a 4.0Ω resistor connected across the output terminals. If the amplifier is then used with negative series voltage feedback so that one tenth of the output signal is fed back to the input, determine the input signal voltage to supply the same output signal current. (16)

Q9.a) Explain the principles of A.C. Motors starting and speed control, including the effect on efficiency. (6)

b) A 3-phase induction motor has a 4-pole, Y-connected stator winding. The motor runs on 50-Hz supply with 200V between lines. The motor resistance and standstill reactance per phase are 0.1 Ω and 0.9 Ω respectively. Calculate (a) the total torque at 4% slip (b) the maximum torque (c) the speed at maximum torque if the ratio of the rotor to stator turns is 0.67. Neglect stator impedance. (10)

Q7. (a) Show by means of diagrams how the center of gravity of the liquid in a partly filled tank moves during rolling. (6)

(b) A box barge is 15 m long, 6 m wide and floats in water of 1.016 t/m³ at a draught of 3 m. 150 tonne of cargo is now added. Calculate the load exerted by the water on the sides, ends and bottom. (10)

Q5. a) What is back emf? Derive the relation for the back emf and the supplied voltage in terms of armature resistance (6)

b) The earth-lamps on a main switchboard comprise two 240 V 60 W lamps connected in the usual manner. The potential difference at the busbars is 220 V. Damage by sea water occurs to a distribution cable so that the insulation resistance to the earth is reduced to 16 ohms and 6 ohms for +ve and -ve cables respectively. Find by calculation:

a) Which of the two lamps burns the brighter:

b) The additional load on the generators occasioned by the fault. The resistance of the cables and the ship’s structure may be neglected, and that of the lamps taken as constant at the value corresponding to the 60 W rating. (10)