DieselShip's Online Content Library

Q6. a) What are the various resistances acting against the motion of the ship? (6)

b) A vessel uses 300 t of fuel on a voyage of 3000 nautical miles at a speed of 12 knots when her displacement is 10000 t. Estimate the fuel required for an estimated voyage of 1500 nautical miles at a speed of 15 knots and displacement of 14000 t. (10)

Q9. a) Name the various types of capacitors? (6)

b) A 500W, 100V bulb is to be connected across 250V, 50Hz mains. Find the value of the capacitor required to be connected in series. (10)

Q7. Ten thousand cubic millimeters of copper are

a) Drawn into a wire 100 metres long,

b) Rolled into a square sheet of 100 mm side. Find the resistance of the wire and the resistance between opposite faces of the plate, if the resistance of the copper is 17 μΩmm or 1.7 x 10-8 ohms-metres. (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)

Q6. a) Describe International protection rating and types of insulation. (6)

(b) A total load of 8000 kW at 0.8 power factor is supplied by two alternators in parallel. One alternator supplies 6000 kW at 0.9 power factor. Find the kVA rating of the other alternator and the power factor. (10)

Q5. With reference to adjoining circuit calculate following

a) Current in each branch of circuit (8)

b) Total current (8)

Q4. a) Explain the significance of the root-mean-square value of an alternating current or voltage waveform. Define the form factor of such a waveform. (6)

b) A total load of 8000 kW at 0.8 power factor is supplied by two alternators in parallel. One alternator supplies 6000 kW at 0.9 power factor. Find the KVA rating of the other alternator and the power factor. (10)

Q7. A. By means of a schematic circuit diagram illustrate the peak rectifier. If the supply voltage is v(t) = Vm Sin wt, what is the voltage across the load resistor?

B. A battery-charging circuit is shown below in Fig. The forward resistance of the diode can be considered negligible and the reverse resistance infinite. The internal resistance of the battery is negligible. Calculate the necessary value of the variable resistance R so that the battery charging current is 1.0 A.

Q10. With reference to 3-phase transformers;

(a) Discuss the essential and desire conditions to be fulfil for operating two three-phase transformers in parallel.

(b) What are the advantages of transformer bank of three 1-phase transformers over a unit three phase transformer of the same kVA rating?

(c) In a 25 kW, 3300/233V, 1- phase transformer the iron and full load copper losses are 350 watts and 400 watts respectively. Calculate the efficiency  at half load, 0.8 p.f.