DieselShip's Online Content Library

Q6. The resistors 5Ω, 7Ω, and 8Ω are connected in series across a voltage source of 10 V. Find the voltage drop across each resistor and also the total power consumed by the circuit. (16)

Q9. a) Differentiate between resistance, induction and impedance in an a.c. circuit. (6)

b) A circuit is made up from resistors of value 2Ω, 4Ω, 5Ω and 10Ω connected in parallel. If the current is 8.6A, find the voltage drop across the arrangement and the current in each resistor. (10)

Q9. a) Explain the effect of bilging a centreline compartment located away from amidships. (6)

B. A ship of 5000 tonne displacement has a double bottom tank 12m long. The ½ breadths of the top of the tank are 5, 4 and 2m respectively. The tank has a watertight centreline division. Calculate the free surface effect if the tank is partially full of fresh water on one side only. (10)

Q6. (a) Define angle of loll (6)

(b) A box barge 60 m long and 10m wide floats at an even keel draught of 4 m. It has a compartment amidships 12 m long. Calculate the new draught if this compartment is laid open to the sea when: (10)

(i) µ is 100%

(ii) µ is 85%

(iii) µ is 60%

Q6. a) How does change to frequency affect the operation of the transformer? What makes this ratio different from the ratio of transformer. (6)

b) The coils A and B are connected in series to 50 Hz mains. The current is 1 A and the voltage across each coil is measured to be 45 V and 70 V respectively. When the coils are connected in a d.c. supply, the current is also 1 A, but the voltages across the coils are now 20 V and 40 V respectively. Find the impedance, reactance and resistance of each coil, the total circuit impedance, the applied a.c. voltage and the power factor of the complete circuit. (10)

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.

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.