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Q5. Fig Q3 shows a single stage transistor amplifier. The voltage between base and emitter is 0.3 V and the d.c. voltage at the output terminals is 8 V. (a) Calculate EACH of the following, assuming the base current is small enough to be neglected: (i) The voltage between emitter and collector; (ii) The power developed in the 150Ωresistor; (iii) The power dissipated in the transistor. (b) Sketch the circuit diagram and show the additional components needed to make the amplifier suitable for amplifying small a.c. signals.

Q10. the following loads are supplied by two alternators running in parallel 1. 1400kw@pf 0.86 lagging 2. 900 kw @ pf 0.8 lagging. 3. 800 kw @ pf unity 4 500kw @pf0.8 leading. If the load on one machine is adjusted to 2100kw @ pf of 0.92 find the load and p.f of the other machine.

Q7. A. Distinguish between power efficiency and all-day efficiency. Why is all-day efficiency considered more reasonable basis for comparison than ordinary efficiency? B. The no-load current of a transformer is 5.0 Amps, power factor 0.25 when supplied at 235 V, 50 Hz. Turns on the primary winding is 200. Calculate A. the maximum value of flux in the core, B. the core loss.

Q10. (a) Explain what is meant by left and right handed propellers, and also explain the rotation of propellers in a twin-screw ship.

(b) A propeller 6m diameter has a pitch ratio of 0.9, BAR 0.48 and, when turning at 110 rev/min, has a real slip of 25% and wake faction 0.30. If the propeller delivers a thrust of 300 KN and the propeller efficiency is 0.65. Calculate:

i. Blade area;

ii Ship speed;

iii. Thrust power;

iv Shaft power

v. Torque.

Q7. A box barge 45 m long and 15 m wide floats at a level keel draught of 2 m in sea water, the load being uniformly distributed over the full length. Two masses, each of 30 tonne, are loaded at 10 m from each end and 50 tonne is evenly distributed between them. Sketch the shear force diagram and give the maximum shear force.

Q10. With reference to the wake of a vessel:

a. Explain Wake fraction and Quasi Propulsive co-efficient(QPC).

b. A ship travelling at 15.5 knots has a propeller of 5.5 m pitch turning at 95 rev/min. The thrust of the propeller is 380 KN and the delivered power 3540 KW. If the real slip is 20% and the thrust deduction factor O.198, calculate the Quasi Propulsive Coefficient (QPC) and the wake fraction.

Q6. A vessel of constant rectangular cross section is 60 m long and 10 m wide, it floats at a level keel draught of 3 m and has a Centre of gravity 2.5 m above the keel. Determine the fore and aft draughts if an empty, full width, fore-end compartment 8 m long is opened to the sea. For simplicity, a permeability of 100 per cent may be assumed. (solve using lost buoyancy method)

Q9. A. Explain the effect on GM during the filing of a double – bottom tank, B. A ship of 8,000 tonnes displacement has KM 7.5m, and KG 7.0m.  A double bottom tank is 12 meters long 15 meters wide and 1 meter deep.  The tank is divided longitudinally at the centre line and both sides are full or small water. Calculate the list if one side is pumped on until it is half empty.

Q8. A. Explain why the amplitude of ship motion should be limited B. A ship of 8100 tonne displacement floats upright in seawater. KG = 7.5m and GM = 0.45m A tank, whose centre of gravity is 0.5m above the keel and 4m from the centreline, contains 100 tonne of water ballast neglecting free face effect, calculate the angle of heel when the ballast is pumped out.

Q8: A box shaped barge of uniform construction is 32 metres long and displaces 352 tonnes when empty, is divided by transverse bulkheads into four equal compartments.  Cargo is loaded into each compartment and level stowed as follows: -

No. 1 hold – 192 tonnes                                               No.2 hold – 124 tonnes

No. 3 hold –272 tonnes                                                No.4 hold – 176 tonnes.

Construct load and shearing force diagram, before calculating the bending moments at the bulkheads and at the position of maximum value; hence draw the bending moment diagram.

Q7. a) Derive the Admiralty Coefficient formula and show how this may be modified to suit a fast ship. (6)

b) A 6m model of a ship has a wetted surface area of 7m2 and when towed in fresh water at

3knots has a total resistance of 35 N. Calculate the effective power of the ship, 120 m long, at its corresponding speed.

n=1.825. f from formula SCF=1.15 (10)

Q10. A. Write shorts notes on various types of DC Motors.

B. A 440V shunt motor takes an armature current of 30A at 700 rev/min. The armature resistance is 0.7ohm. If the flux is suddenly reduced by 20 per cent, to what value will the armature current rise momentarily? Assuming unchanged resisting torque to motion, what will be the new steady values of speed and armature current? Sketch graphs showing armature current and speed as functions of time during the transition from initial to final, steady-state conditions.