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Q9. (a) Explain what is meant by phase difference between voltage and current values. (6)
(b) An inductance coil has a resistance of 19.5Ω and when connected to a 220V, 50Hz supply, the current passing is 10A. Find the inductance of the coil. (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)

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.

Q9.  A. Explain how the voltage regulation of a transformer is defined. Is this quantity large or small for the iron-core transformer? Explain B. A single-phase transformer has 480 turns on the primary and 90 turns on the secondary. The mean length of the flux path in the core is 1.8m and the joints are equivalent to an air gap of 0.1mm. The value of the magnetic field strength for 1.1T in the core is 400 A/m, the corresponding core loss is 1.7W/Kg at 50Hz and the density of the core is 7800 Kg/m3

Q7. A. Derive an expression for the e.m.f induced in an a.c. generator. B. A 3000 KVA, 6 pole alternators runs at 1000 r.p.m in parallel with other machines on 3300 V bus-bars. The synchronous reactance is 25%. Calculate the synchronizing power for one mechanical degree of displacement and the corresponding synchronizing torque.