1. Select the correct answer from the given four alternatives for the following multiple choice type questions:

Wet Bulb temperature indicates the temperature of

water

air

nitrogen

air, when the bulb of the thermometer is covered with wet wick or cloth

A ton of refrigeration is

60 kcal/min

75 kcal/min

3000 kcal/hr

3500 kcal/hr

According to Boyle's law

at constant temperature, pressure is proportional to the volume.

at constant temperature, pressure is inversely proportional to the volume.

pressure is proportional to the volume irrespective of its temperature.

None of the above

Two stroke engines offer their advantage due to

low initial cost and lower mechanical efficiency

low initial cost and higher mechanical efficiency

low initial cost and higher thermal efficiency

None of the above

Mean effective pressure in a cylinder is

Work done per cycle/Stroke length

Area of indicator diagram/Length of the diagram

Stroke Volume/Work done per cycle

None of the above

Main function of piston in I.C. engines is to

Rotate the engine

Complete the strokes

Seal the gases

Increase the power

Which one of the following is not a component of vapour compression refrigeration system

Compressor

Condenser

Expansion device

Separator

A capacitor draws a current of 5 rnA from 200 50 Hz A.C. If it draws from 40 400 Hz supply, current will be

2 mA

4 mA

8 mA

16 mA

Which one of the following is not a merit of three-phase system over single-phase system?

More kVA rating

Less conducting material required for lines

More expensive

Economic

Which transformer is used in street lighting?

Constant current transformer

Tapped transformer

Auto transformer

Potential transformer

A 4·54 MF capacitor is connected with 230 V alternating voltage and 50 Hz frequency. What will be the current in ampere through the capacitor?

0.28 A

0·32 A

0·36 A

0·40 A

A 5 kW, 50 Hz, 6-pole slip ring induction motor is running at a speed of 9600 rpm. Percentage slip will be



(in





Specific gravity reading by hydrometer of a full charged battery is

1·10

1·18

1·20

1·28

Phase difference in coils of a three-phase alternator is

600

1200

1800

2400

2. Attempt any two of the following:

Explain the following terms as applied to I.C. Engine:

Specific fuel consumption

Mechanical efficiency

Volumetric efficiency

Relative efficiency

Indicated thermal efficiency

Brake thermal efficiency

Knocking

Discuss the working of a four-stroke Diesel Engine with a suitable diagram.

Describe an electric chain hoist. How can this hoist be used to move the load along the length of workshop?

3. Answer any two of the following:

4 kg of air at pressure of 7 bar occupies a volume of 0.28 m^3. This air is expanded to a volume of 1·4 m^3 following a law pV^1·2 =constant. Find:

Final temperature

The work done

Explain the following:

Sensible and Latent heat

Coefficient of performance of heat engine and heat pump

Diameter of cylinder and stroke of the piston of an Otto cycle petrol engine are 10 cm and 16 cm respectively. Clearance volume is 250 cm^3. Find out the air standard efficiency of the engine. (take v =1·4)

4. Attempt any two of the following:

Define Ohm's law. In the circuit given in Figure calculate the current through each battery and potential difference between the terminals E and F of the given circuit.

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A 25 kVA transformer has 500 turns on the primary and 50 turns on the secondary winding. The primary is connected to 3300 50 Hz supply. Find the full load primary and secondary currents, the secondary emf and the maximum flux in the core. Neglect leakage and no-load primary current.

Three capacitors of capacity 10, 20 and 40 MF are placed in series across a 300 V source. Determine

equivalent capacitance of the combination,

charge on each capacitor, and

voltage drop across each capacitor.

5. Attempt any two of the following:

Determine the value of the torque established by the armature of a 4-pole motor having 744 conductors, wave wound. The flux per pole is 2·4 x Weber and the total armature current is 50 amperes.

Explain the necessity of transformer ill power system. Explain the principle of working of a transformer.

A 400 V shunt generator has a full-load current of 200 its armature resistance is 0·06 ohms and field resistance, 100 ohms, the stray losses are 2000 W. Find the h.p. of its prime mover, when it is delivering full load and find the load for which the efficiency of the generator is maximum.