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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)

Q8. (a) Describe the effect of running an induction motor on reduced voltage.

(b) A motor takes a current of 60 amperes at 230 volts, the power input being 12 kW. Calculate the power component and the reactive component of the input current. (10)

Q8. (a) What is a 'mast riser' and what is the purpose of it? (6)

(b) A ship 96 m long is floating at 5m fwd draft and 6.4 m aft draft, MCTC 180 tm, TPC 16. COF is 2 m abaft of midships. Find the location where a weight of 50t should be placed so as to keep the aft draft constant. (10)

Q5. a) Describe an accurate method of comparing the capacities of two condensers. (6)

b) A resistor of 0.525 ohms is connected to the terminals of a battery consisting of 4 cells, each e.m.f. 1.46 V joined in parallel. The circuit current is found to be 0.8 A. Find the internal resistance of each cell. (10)

Q8. a) What is a Zener diode? (6)

b) Find the generated e.m.f./conductor of a 6-pole d.c. generator having a magnetic flux/pole of 64m Wb and a speed of 1000 rev/min. If there are 468 conductors, connected in six parallel circuits, calculate the total generated e.m.f. of the machine. Find also the total power developed by the armature when the current in each conductor is 50 A. (10)

Q5. A circuit has a resistance of 3Ω and an inductance of 0.01H. The voltage across its ends is 60V and the frequency is 50Hz. Calculate

a) The impedance (6)

b) The power factor (5)

c) The power absorbed. (5)

Q5. A) Explain three methods of overcurrent protection for electric circuit (6)

b) A circuit has a resistance of 3Ω inductance of 0.01H. The voltage across its end is 60V and the frequency is 50Hz. Calculate,

(i) the impedance (4)

(ii) the power factor (3)

(iii) the power absorbed. (3)

Q6. (a) Explain in brief the term 'bulwark' and 'freeing port'. (6)

(b) A ship has 300 t of cargo in the hold, 24 m forward of the midships. The displacement of the vessel is 6000 t and its centre of gravity is 1.2 m forward of midships. Find the new position of the centre of gravity if this cargo is moved to an after hold, 40 m from midships. (10)

Q6. A. What are the characteristics of PN junction diode? Point out its specifications. Also point out the significance of dynamic and static resistances. (6)

B. Draw the circuit of Half-wave rectifier and its output waveform. A diode whose internal resistance is 20 Ω is to supply power to 1000 Ω load from 110 V (RMS) source. Calculate

(i) Peak load current, (ii) DC load current, (iii) AC load current. (10)

Q7. With reference to adjoining circuit calculate following. (a) Current in each branch of circuit. (b) Total current.

Q7. A. Describe how protection against short circuit is provided in a 3 phase induction motor circuit.

B. Explain how rotating magnetic field is produced in three phase winding with three phase supply. A 4-pole, 3-phase induction motor operates from a supply whose frequency is 50 Hz. Calculate

(i) Speed at which the magnetic field of the stator is rotating,

(ii) speed of the rotor when the slip is 0.04,

(iii) the frequency of the rotor current when the slip is 0.03.