DieselShip's Online Content Library

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)

Q6. (a). Explain the significance of the root- mean- square value of an alternating current or voltage waveform; Define the form factor of such a wave form.

(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.

Q7. With reference to A.C Distribution system:

A. Define power factor and explain the effects of low power factor.

B. 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.

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.

Q8. A ship 160m long and 8700 tonne displacement floats at a waterline with

While floating at this waterline, the ship develops a list of 10° due to instability. Calculate the negative metacentric height when the vessel is upright in this condition

Q7. A. Describe stability requirement for dry-docking. B. A ship of 8000 tonne displacement, 110m long, floats in sea water of 1.024t/m3 at draughts of 6m forward and 6.3 m aft. The TPC is 16, LCB 0.6 m aft of midships, LCF 3m aft of midships and MCT1cm 65 tonne m, the vessel now moves into fresh water of 1.000t/m3. Calculate the distance a mass of 50 tonne must be moved to bring the vessel to an even keel and determine the final draught.