Mock Test: SSC JE (ME)- 1 - Mechanical Engineering MCQ

T₁ = 27 +273 =300 K

V₁ =V

V₂=3V

T₂ =?

use  P₁V₁/T₁  = P₂V₂/T₂

GIVEN P₁ =P₂

SO V₁/T₁ =V₂/T₂

V/300 = 3V/T₂

 T₂ =900K

= 627°C

Law of thermodynamics is the basis for measurement of temperature and setting its scale. In simple word, Zeroth law of thermodynamics says that “When two bodies are separately in thermal equilibrium with the third body, then the two are also in thermal equilibrium with each other.”

As the hot coffee remains hot for a long time so neither heat nor mass is exchanged with the surroundings and hence it is an example of isolated system.

Q_{supplied = 60KJ}

_{du= -30 KJ}

_{from first law of thermo=}

_{dQ = du + dW}

_{60 = -30 + dW}

_{dW = 90 KJ}

The work is the path function so the work transfer between the system and the surrounding depend on the path that followed by tha system.

1 joule (J) = 1.00 newton meters (N-m)

General gas equation

pv=mrt

at absolute zero kelvin temp.
pressure =zero

that means

0×v= mr×0

therefore volume will be zero at absolute zero kelvin temp.

According to Avogadro's law ,the volume of a gram mole of all gases at the pressure of 760 mm of Hg and temperature of 0 degree centigrade is same and is equal to 22.4 litres.

dU + PdV = dH which is enthalpy

No engine working between two given temperatures can be more efficient than a reversible engine working between the same two temperatures and that all the reversible engines working between the same two temperatures have the same efficiency, whatever the working substance may be.

The leaks in a refrigeration system using Freon are detected by Halide torch which on detection produces greenish flame lighting

The hydrogen passes across the surface of the ammonia. It lowers the ammonia vapor pressure enough to allow the liquid ammonia to evaporate. The evaporation of the ammonia extracts heat from the evaporator. This, in turn, extracts heat from the food storage space, lowering the temperature inside the refrigerator.

 Cetane and alpha-methyl naphthalene are the reference fuels taken for cetane rating.

For maximum power, slightly rich mixture is required in order to burn more fuel and get energy.

The air fuel ratio for different operations is given below

Idling – 10

Cruising – 16

Maximum Power – 13

Cold Starting – 3

A spark plug gap is kept from- 0.3-0.7 mm because 0.3-0.7 is perfect gap for making spark in spark plug.

Ignition quality of petrol is expressed by octane number and that of diesel by cetane number.

Economizer is boiler accessory and others are mounting