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

If the temperature remains constant, the volume of the given mass of a gas is inversely proportional to the pressure. This is known as

Charles' Law

Boyle's Law

Joule's Law

Gay-Lussac's Law

In which of the following processes, will the internal energy of a system remain constant?

Isothermal

Adiabatic

Isobaric

Isochoric

A process in which the gas is heated or expanded in such a way that the product of its pressure and volume remains constant is called

Isothermal process

Isobaric process

Adiabatic process

Polytropic process

An adiabatic process occurs at constant

temperature

pressure

heat

None of the above

The air standard efficiency of an Otto cycle is given by

1 - 1

1 1

1

1

where r =compression ratio, y Cp-/Cv

The gas law =constant) is true for

Isothermal process

Adiabatic process

Both isothermal and adiabatic processes

Neither isothermal nor adiabatic process

The actual power supplied by engine crank shaft is called

Indicated power

Brake power

Frictional power

None of the above

An electric kettle rated at 220 2·2 kW, works for 3 hours. The current drawn will be

2 amp

10 amp

25 amp

30 amp

A wire of resistance R is cut into n equal parts. These parts are then connected in parallel. The equivalent resistance of the combination will be

nR

R/n

n/R



The resistance of an ideal voltmeter is

Zero

Infinity

lOO ohms

500 ohms

One ton of refrigeration is equal to

1000kJ

3.5kW

1kW

1000 kW

The appropriate material to be used in the construction of resistance boxes, out of the following, is

Copper

Iron

Manganin

Aluminium

Three resistances each of4 .0 are connected to form a triangle. The resistance between any two terminals is

12.0 ohm

6.0 ohm

8/3 ohm

2 ohm

In a pure inductive circuit with a.c. source, the current lags behind the emf by

1t

21t

1d^2

1d^4

2. Attempt any two of the following:

Explain briefly the simple vapour compression refrigeration system with the help of a neat diagram.

0·1 m^3 of all-at a pressure of 1·5 kgf/cm^2 is expanded isothermally to 0·5 m^3. Calculate the final pressure of the gas and heat supplied during the process. Also calculate the work done during the expansion of gas.

Explain with suitable sketches the working of a four-stroke Otto cycle engine.

3. Attempt any two of the following

Explain with a neat diagram the working of summer air-conditioning system.

A certain gas occupies a space of 0·3 m^3 at a pressure of 2 kgf/cm^2 and a temperature of 77°C. It is heated at a constant volume, until the pressure is 7 kgf/cm^2. Determine the

temperature at the end of the process,

mass of the gas,

change in internal energy, and

change in enthalpy.

Assume Cp =1·005 kJ/kg°K, Cv=0·712 kJ/kg°K and R =287 J/kg°K

Discuss briefly the comparison between four-stroke and two-stroke engines.

4. Answer any two of the following:

A resistance A of 3 ohms in parallel with produces a current of 3 Amperes when connected across a 6 V battery. Find

the current in A and

the resistance of B.

What resistance X must be put in series with AB combination to reduce the current to 2 Amperes?

State Faraday's law of electromagnetic induction.

Three capacitors of capacitance 10, 20 and 40 u.F are placed in series across a 350 V source. Determine the

Equivalent capacitance of the combination,

Charge on each capacitor,

Voltage drop across each capacitor, and

Total stored energy.

5. Answer any two of the following:

Deduce the expression for the emf induced by the operation of a D.C. generator.

What emf will be generated in an 8-pole wave wound D.C. generator, if it is rotated at 500 RPM The flux per pole is 0·05 Weber and the number of armature conductors is 960.

Find the inductance of an inductor which draws a current of 1·1 A when connected to 230 50 Hz voltage. What current will it draw, if the supply voltage is changed to 150 25 Hz?