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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.

Q10. A. Why is a synchronous motor not self-starting? What are the various ways in which it can be started?

B. A 500V, single phase synchronous motor gives a net output mechanical power of 7.46kW and operates at 0.9 power factor lagging. Its effective resistance is 0.8 . If the iron and friction losses are 500 w and excitation losses are 800w, calculate the armature current and the commercial efficiency.

Q9. A. Briefly describe the maintenance routines carried out for emergency batteries onboard.

B. A power of 36 W is to be dissipated in a register connected across the terminals of a battery, having emf of 20V and an internal resistance of 1Ω. Find (i) What value of resistance will satisfy this condition. (ii) The terminal voltage of the battery for each of the resistances and (iii) The total power expenditure in each case.

Q6. For the network shown in Fig.Q1 calculate each of the following: (a) The current drawn from each battery; (b) The potential difference across the 40Ωresistor and across the 50Ωresistor; (c) The power dissipated in the 60Ωresistor.