DieselShip's Online Content Library

Q9. a) Explain why an unstable ship is dangerous. (6)

(b) A vessel travelling at 17 knots turns with a radius of 450 m when the rudder is put hard over. The centre of gravity is 7 m above the keel, the transverse metacentre 7.45 m above the keel and the centre of buoyancy 4 m above the keel. If the centripetal force is assumed to act at the centre of buoyancy, calculate the angle of heel when turning. The rudder force may be ignored. (10)

Q7. A box barge 25 m long and 4 m wide floats in fresh water at a draught of 1.2 m and has an empty mid length compartment 5 m long. The bottom of the barge is lined with teak (rd 0.805) 120 mm thick. After grounding all the teak is torn off and the centre compartment laid open to the sea. Calculate the final draught. (16)

Q7. a) What is self-induction? (6)

b) A coil of 800 turns is wound on a wooden former and a current of 5A is passed through it to produce a magnetic flux of 200 micro-webers. Calculate the average value of e.m.f. induced in the coil when the current is

i) switched off in 0.08 seconds

ii) reversed in 0.2 seconds. (10)

Q9). a) Define Work, power and efficiency (6)

b) A battery is charged with a constant current of 16 amperes for 11 hours after which time it is considered to be fully charged, its voltage per cell being recorded as 2.2V. Find its ampere hour efficiency if it is

(1) Discharged at a rate of 16 amperes for 10 hours, and

(2) 28 amperes for 4 hours.

In either case discharge was discontinued when the voltage per cell fell to 1.8 V.  (10)

Q8. (a) Define work, Power and Efficiency (6)
(b) A shunt motor has an armature resistance of 0.2 ohms and with an armature current of 120 amperes runs at 750 r.p.m. off a 400-volt supply. Calculate the speed and armature current of the motor if the flux per pole is reduced to 75 per cent of its initial value, the total torque remaining unaltered. (10)

Q7. The loads of a 4-wire, 3-phase systems are: Red line to neutral current = 50 A, power factor of 0.707 (lagging) Yellow line to neutral current = 40 A, power factor of 0.866 (lagging) Blue line to neutral current = 40 A, power factor 0.707 (leading). Determine the value of the current in the neutral wire. (16)

Q7. (a) What are the different types of stern used in ship construction? (6)

(b) A ship consumes 360t of fuel, stores and water when moving from sea water of 1.025 t/m3 into fresh water of 1.000 t/m3 and on arrival it is found that the draught has remained constant. Calculate the displacement in sea water. (10)

Q4. a) Why is a synchronous motor not self-starting? What are the various ways in which it can be started? (6)

b) A coil has a resistance of 4 ohms and an inductance of 0.00954 henry. Calculate the power the coil will absorb and its power factor when it is connected to a 100-volts 50-cycle supply. (10)

Q7. a) Explain what do you understand by the term ‘transducer’? (6)

b) A coil of resistance 10 ohms and inductance 100mH is connected in series with two parallel capacitors each of value 100 mF across a 250 V, 50Hz supply. determine (10)

i) The circuit current

ii) The total power factor

iii) The power taken from the supply.

Q6. A 100 KVA, 2400/240 V, 50 Hz, 1-phase transformer has no- load current of 0.64 A and a core loss of 700 W, when its high voltage side is energized at rated voltage and frequency . calculate the two components of no-load current. If this transformer supplies a load current of 40 amp at 0.8 lagging power factor at its low voltage side, determine the primary current and its power factor. Ignore leakage impedance drop. (16)

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. A. Explain the effect on GM during the filing of a double – bottom tank. (6)
B. The length of a ship is 18 times the draught. while the breadth is 2.1 times the draft. At the load water plane, the water plane area co-efficient is 0.83 and the difference between the TPC in sea water and the TPC in fresh water is 0.7. Determine the length of the ship and TPC in fresh water.