Olete.in – MCQs, Mock Tests & Government Job Prep | IIT JEE IIT JEE Heat And Thermodynamics

When a metal rod is heated it expands because:

1. the size of its atoms increases
2. the distance among its atoms increases
3. atmospheric air rushes into it
4. the actual cause is still unknown

✅ Correct Answer: 2

Two vessels having equal volume contain molecular hydrogen at one atmosphere and helium at two atmospheres respectively. If both samples are at the same temperature the mean velocity of hydrogen molecules is:

1. equal to that of helium
2. twice that of helium
3. half that of helium
4. v2 times that of helium

✅ Correct Answer: 4

At a certain temperature, hydrogen molecules have rms velocity 2 km/s. The rms velocity of the oxygen molecules at the same temperature is:

1. 2 km/s
2. 8 km/s
3. 0.5 km/s
4. 1 km/s

✅ Correct Answer: 3

If the heat of 110 J is added to a gaseous system and change in internal energy is 40 J, then the amount of external work done is:

1. 140 J
2. 70 J
3. 110 J
4. 150 J

✅ Correct Answer: 2

The internal energy U is a unique function of any state because change in U: depend upon path corresponds to an adiabatic process

1. does not depend upon path
2. depend upon path corresponds to an adiabatic process
3. corresponds to an isothermal process
4. none of the above

✅ Correct Answer: 1

In a thermodynamic system working substance is ideal gas its internal energy is in the form of:

1. kinetic energy only
2. kinetic and potential energy
3. potential energy
4. none of the above

✅ Correct Answer: 2

Gas exerts pressure on the walls on the container because:

1. gas has weight
2. gas molecules have momentum
3. gas molecules collide with each other
4. gas molecules collide with the walls of the container

✅ Correct Answer: 4

For a perfect gas if:

1. P and V are given T is uniquely determined
2. T is given P is uniquely determined
3. T is given V is uniquely determined
4. T is given P and V both are uniquely determined

✅ Correct Answer: 1

The respective speeds of five molecules are 2, 15, 16, 16 and 12 km/s, the most probable speed in km/s will be:

1. 2
2. 1.58
3. 1.6
4. 1.31

✅ Correct Answer: 4

Air in a cylinder is suddenly compressed by a piston which is then maintained at the same position. With the passage of time: the pressure decreases

1. the pressure increases
2. the pressure remains the same
3. the pressure may increase or decrease depending on the nature of the ga
4. none of them

✅ Correct Answer: 2

Which of the following statements is correct for any thermodynamic system?

1. The internal energy changes in all processes Internal energy and entropy are state functions
2. The change in entropy can never be zero
3. The work done in an adiabatic process is always zero
4. none of them

✅ Correct Answer: 2

If a system undergoes contraction of volume, then the work done by the system is:

1. positive
2. negative
3. negligible
4. zero

✅ Correct Answer: 2

Heat given to a body which raises its temperature by 1degree centigrade is:

1. water equivalent
2. thermal capacity
3. specific heat
4. temperature gradient

✅ Correct Answer: 2

Significant motion for the molecules of a monoatomic gas corresponds to:

1. translatory
2. vibratory
3. rotatory
4. none of these

✅ Correct Answer: 1

If the door of a refrigerator is kept open then which of following is true?

1. Room is cooled
2. Room is heated
3. Room is either cooled or heated
4. Room is neither cooled nor heated

✅ Correct Answer: 2

The most efficient heat engine is one which is:

1. reversible
2. irreversible
3. driven by high speed diesel
4. none of the above

✅ Correct Answer: 1

A gas is filled in a cylinder Its temperature is increased by 20% on kelvin scale and volume is reduced by 10% How much percentage of the gas has to leak for pressure to remain constant?

1. 30%
2. 40%
3. 15%
4. 25%

✅ Correct Answer: 4

When rod is heated but prevented from expanding, the stress is independent of:

1. material of the rod
2. rise in temperature
3. length of rod
4. none of these

✅ Correct Answer: 3

9.For an isolated system:

1. volume is constant
2. pressure is constant
3. all of these
4. 20.Internal energy of ideal g

✅ Correct Answer: 4

Internal energy of ideal gas depend on: only volume none of these

1. only pressure
2. temperature is constant
3. only temperature
4. none of these

✅ Correct Answer: 3

The molecular weight of gas is 44. The volume occupied by 2.2 g of this gas at 0 degreeCentigrade and 2 atm pressure, will be: 2.4 L

1. 0.56 L
2. 1.2 L
3. 2.4 L
4. 5.6 L

✅ Correct Answer: 1

If mass-energy equivalence is taken into account, when water is cooled to form ice, the mass of water should:

1. increase
2. remain unchanged
3. decrease
4. first increase then decreas

✅ Correct Answer: 1

Which statement is incorrect?

1. All reversible cycles have same efficiency
2. Reversible cycle has more efficiency than an irreversible one
3. Carnot cycle is a reversible one
4. Carnot cycle has the maximum efficiency in all cycles

✅ Correct Answer: 1

A block of mass 100 g slides on a rough horizontal surface If the speed of the block decreases from 10 m/s to 5 m/s the thermal energy developed in the process is:

1. 3.75 J
2. 37.5 J
3. 0.375 J
4. 0.75 J

✅ Correct Answer: 1

The process in which the heat is not transferred from one state to another, is: isothermal process

1. isothermal process
2. adiabatic process
3. isobaric process
4. isochoric process

✅ Correct Answer: 2

Heat cannot be itself flow form a body at lower temperature to a body at higher temperature is a statement of consequence of:

1. second law of thermodynamics
2. conservation of momentum
3. conservation of mass
4. thermodynamics

✅ Correct Answer: 1

The specific heat of gas in an isothermal process is:

1. zero
2. infinite
3. first law of
4. remains constant

✅ Correct Answer: 2

The standard fixed point for temperature measurement is used these day is:

1. melting point of ice at STP
2. that temperature at which ice water and water vapour coexist
3. that temperature at which pure ice and pure water coexist
4. none of these

✅ Correct Answer: 2

Which of the following parameters does not characterize the thermodynamic state of matter?

1. Volume
2. Temperature
3. Pressure
4. Work

✅ Correct Answer: 4

The scale of temperature on which the temperature are only positive is:

1. Fahrenheit
2. Celsius
3. Kelvin
4. Reaumur

✅ Correct Answer: 3

The wax melts up to lengths 105 cm and 60 cm for two indentical rods of different metals in Ingen Hausz experiment The ratio of thermal conductivities of the two metals is

1. 7:04
2. 4:07
3. 49:16:00
4. 16:49

✅ Correct Answer: 3

When a gas is allowed to expand suddenly into a vacuum chamber, then:

1. heat supplied is zero
2. temperature remains constant
3. volume does not change
4. both A and C are correct

✅ Correct Answer: 2

Molar heat capacity is directly related to:

1. temperature
2. heat energy
3. molecular structure
4. mass

✅ Correct Answer: 3

At what temperature is the effective speed of gaseous hydrogen molecules equal to that of oxygen molecules at 47 degreeCentigrade?

1. 50 K
2. 20 K
3. 40 K
4. 100 K

✅ Correct Answer: 2

When water is heated from 0 degree Centigrade to 10 degree centigrade its volume:

1. increases
2. decreases
3. remains unchanged
4. first decreases then increases

✅ Correct Answer: 4

If r, a and t represent the reflection coefficient, absorption coefficient and transmission coefficient respectively, then for a perfectly black body

1. r = 0, a = 1, t = 0
2. r = 1, a = 0 and t = 0
3. r = 0, a = 0, t = 0
4. r = 0, a = 0 and t = 0

✅ Correct Answer: 1

During adiabatic change, specific heat is:

1. zero
2. greater than zero
3. less than zero
4. infinity

✅ Correct Answer: 1

Unsaturated vapour obeys:

1. Ideal gas law
2. Van der Walls law
3. Boyles law
4. Gay-Lussacs law

✅ Correct Answer: 1

What work will be done, when 3 moles of an ideal gas are compressed to half the initial volume at a constant temperature of 300 K? J

1. -5188 J
2. 5000 J
3. 5188 J
4. -5000 J

✅ Correct Answer: 1

When without change in temperature a gas is forced in a smaller volume, its pressure increases because its molecules:

1. strike the unit area of the container wall more often
2. strike the unit area of the container wall at higher speed
3. strike the unit area of container wall with greater force
4. have more energy

✅ Correct Answer: 1

If l is the length, A is the area of cross-section and K the thermal conductivity, then the thermal resistance of the block is given by

1. Kl / A
2. I / KA
3. AK / l
4. A / Kl

✅ Correct Answer: 2

The pressure of a gas kept in an isothermal container is 200 kPa If half the gas is removed from it, the pressure will be:

1. 100 kPa
2. 200 kPa
3. 400 kPa
4. 800 kPa

✅ Correct Answer: 1

Two thermometers are constructed in such a way that one has a spherical bulb and other has elongated cylindrical bulb The bulbs are made of same material and thickness Then:

1. spherical bulb will respond more quickly to temperature changes
2. cylindrical bulb will respond more quickly to temperature changes
3. both bulbs will respond same to temperature changes
4. none of both bulbs respond to temperature changes

✅ Correct Answer: 2

The temperature of a substance increases by 27 degree Centigrade On the Kelvin scale this increase is equal to:

1. 300 K
2. 2.46 K
3. 27 K
4. 7K

✅ Correct Answer: 3

During an isothermal expansion of an ideal gas:

1. its internal energy decreases
2. its internal energy does not change
3. the work done by the gas is equal to the quantity of heat absorbed by it
4. both B and C are correct

✅ Correct Answer: 4

Pyrometer is an instrument used to measure:

1. High temperatures
2. Low temperatures
3. Specific heat
4. Latent heat

✅ Correct Answer: 1

The thermal resistance of two blocks connected in series will be, if their separate thermal resistances are 2 and 3 is

1. 1
2. 6
3. 5
4. 1.5

✅ Correct Answer: 3

If gas is compressed adiabatically:

1. the internal energy of gas increases
2. the internal energy of gas decreases
3. the internal energy of gas does not change
4. the work done is positive

✅ Correct Answer: 1

Which of the following quantities is zero on an average for the molecules of an ideal gas in equilibrium? Density

1. Kinetic energy
2. Momentum
3. Density
4. Speed

✅ Correct Answer: 2

Which of the following carries anomalous expansion?

1. Mercury
2. Water
3. Copper
4. Sodium

✅ Correct Answer: 2

During severe winter in the low temperature zones of the world, the superficial parts of the lakes are frozen leaving water below. That the freezing at the bottom is prevented because:

1. the conductivity of ice is low
2. the water has large latent heat of fusion
3. the water has large specific heat
4. the temperature of the earth at the bottom of lake is high

✅ Correct Answer: 1

The ratio of thermal capacities of two spheres A and B, if their diameters are in the ratio 1: 2, densities in the ratio 2: 1 and the specific heats in the ratio of 1: 3 will be:

1. 1:06
2. 1:12
3. 1:03
4. 1:04

✅ Correct Answer: 2