DieselShip's Online Content Library

Q7. A resistor of ohm value 3 ohms is connected in series with a coil of inductance 0.1 H and resistance 1 ohm. If 100 V at a frequency of 50 Hz is applied to the circuit find the current flowing.

Q8. (a) Explain various powers and efficiencies in the Propulsion plant of a ship (6)
(b) A vessel with a displacement of 12250 t burns 290 t of fuel while travelling at a speed of 15 knots on a voyage of 2850 nautical miles. On a voyage of 1800 nautical miles at a speed of 13 knots and a displacement of 14200 t, estimate the quantity of fuel that will be burnt. (10)

Q7.  The pitch of a propeller is measured by means of a batten and cord. The horizontal ordinate is found to be 40 cm while the vertical ordinate 1.15 m at a distance of 2.6 m from the centre of the boss. calculate the pitch of the propeller and the blade width at that point. (16)

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. A 72 KVA transformer supplies a heating and lighting load of 12 KW at unity power factor and a motor load of 70 kVA at 0.766 (lagging) power factor: Calculate the minimum rating of the power-factor improvement capacitors which must be connected in the circuit the ensure that the transformer does not become overloaded. (10)

Q7. a) Describe the principle of variable-capacitance transducer. (6)

b) A coil of resistance 10 ohms and inductance 100mH is connected in series with two parallel capacitors each of value 100 mF across a 250 V, 50Hz supply. determine (10)

i) The circuit current

ii) The total power factor

iii) The power taken from the supply.

Q9. a) What is meant by the term ‘back e.m.f.’ as applied to an electric motor? (6)

b) A 40 kW,220V shunt motor has a full-load efficiency of 90 per cent, an armature resistance of 0.075 ohms and a shunt motor-field resistance of 55 ohms. When ‘at starting’, the starter handle is moved onto the first stud, it is desired to limit the current, through the armature to 1.5 times the value which it has when the motor is on full load. What must be the total value of the starting resistance? If, on overload, the speed falls to 90 per cent of its normal full-load value. What would be the armature current? Neglect the effect of armature reaction. (10)

Q9. (a) Describe the effect of running an induction motor on reduced voltage (6)

(b) A 90V D.C. generator is used to charge a battery of 40 cells in series, each cell having an average e.m.f. of 1.9 V and an internal resistance of 0.0025 Ω. If the total resistance of the connecting cells is 1Ω, calculate the value of the charging current (10)

Q7. (a) What is Freeboard of a Ship? Why oil tankers have less freeboard? (6)

(b) A box barge 25 m long and 4 m wide floats in fresh water at a draught of 1.2 m and has an empty mid length compartment 5m long. The bottom of the barge is lined with teak (rd 0.805) 120mm thick. After grounding all the teak is torn off and the centre compartment laid open to the sea. Calculate the final draught. (10)

Q6. A) With the aid of delta and star connection diagrams, state the basic equation from which the delta-star and star- delta conversion equation can be derived. (6)
B) Three batteries A, B, and C have their negative terminals connected together. Between the positive terminals of A and B there is a resistor of 0.5 ohm and between B and C there is a resistor of 0.3 ohm
Specifications of the three batteries are given below.
Battery A 105 V, Internal resistance   0.25 ohm
Battery B 100 V, Internal resistance   0.2 ohm
Battery C   95 V, Internal resistance   0.25 ohm
Determine the current values in the two resistors and the power dissipated by them. (10)

Q9. A. List the factors that determine the maximum developed torque of the induction motor. (6)

B. The primary and secondary windings of a 500 KVA transformer have resistance of 0.42 Ω and 0.0019 Ω respectively. The primary and secondary voltages are 11000 V and 415 V respectively and the core loss is 2.9 kW, assuming the power factor of the load to be 0.8. Calculate the efficiency on (i) Full load (ii) Half load. (10)

Q10. A. Compare the effectiveness of a current limiting circuit breaker with that of a HRC fuse.

B. A coil having a resistance of 10 Ohm, and an inductance of 0.15 H is connected in series with a capacitor across a 100V, 50Hz supply. If the current and the voltage are in phase what will be the value of the current in the circuit and the voltage drop across the coil?

Q6. A. Explain what is meant by the terms wave form, frequency and average value. (6)

B. A moving coil ammeter, a thermal ammeter and a rectifier are connected in series with a resistor across a 110 V sinusoidal a.c. supply. The circuit has a resistance of 50 𝛀 to current in one direction and, due to the rectifier, an infinite resistance to current in the reverse direction. Calculate:

(i) The readings on the ammeters.

(ii) The form and peak factors of the current wave. (10)