A black body at a temperature of 227Â°C radiates heat at the rate of 20 cal m-2s-1. When its temperature rises to 727Â°C, the heat radiated will be

1.40 units

2.160 units

3.320 units

4.640 units

**Posted Date**:-2021-12-23 14:28:42

A black body at hot temperature at 227Â°C radiates heat at a rate of 5 cal/cmÂ²s. at a temperature of 727Â°C the rate of heat radiated per unit area will be

1.50 cal/cmÂ²s

2.250 cal/cmÂ²s

3.80 cal/cmÂ²s

4.100 cal/cmÂ²s

**Posted Date**:-2021-12-23 14:08:32

A body cools from 50Â°C to 46Â°C in 5 minutes and to 40Â°C in the next 10 minutes. The surrounding temperature is

1.30Â°C

2. 28Â°C

3. 36Â°C

4.32Â°C

**Posted Date**:-2021-12-23 14:09:16

A bucket full of hot water is kept in a room and it cools from 75Â°C to 70Â°C in t1 minutes from 70Â°C to 65Â°C in t2 minutes and from 65Â°C to 60Â°C in t3 minutes; then

1. t1 â€“ t2 = t3

2.t1 < t2 < t3

3.t1 > t2 > t3

4. t1 < t2 > t3

**Posted Date**:-2021-12-23 14:10:42

A Carnot engine whose sink is at 300 K has an efficiency of 40%. By how much should the temperature of source be increased, so as to increase its efficiency by 50% of original efficiency?

1.275 K

2.325 K

3.250 K

4.380 K

**Posted Date**:-2021-12-23 14:34:28

A cup of tea cools from 80Â°C to 60Â°C in one minute. The ambient temperature is 30Â°C. in cooling from 60Â°C to 50Â°C, it will take.

1.50 sec

2.90 sec

3.60 sec

4.30 sec

**Posted Date**:-2021-12-23 14:13:43

A metal piece heated to T1Â°K. The temperature of the surrounding is T2Â°K. the heat in the surrounding due to radiation is proportional to

1.(T14 â€“ T24)

2. (T1 â€“ T2)4

3.(T14 + T24)

4.(T13 â€“ T23)

**Posted Date**:-2021-12-23 14:19:00

A person with dark skin as compared to a person with white skin will experience

1.Less heat and less cold

2.More heat and more cold

3.More heat and less cold

4.Less heat and more cold.

**Posted Date**:-2021-12-23 14:12:50

A resonance air column of length 40 cm resonates with a tuning fork of frequency 450 Hz. Ignoring end correction, the velocity of sound in air will be

1. 720 m/s

2.820 m/s

3.920 m/s

4.1020 m/s

**Posted Date**:-2021-12-23 15:28:58

A room temperature the r.m.s. velocity of the molecules of a certain diatomic gas is found to be 1930 m/sec. the gas is

1. HÂ²

2.FÂ²

3.OÂ²

4.ClÂ²

**Posted Date**:-2021-12-23 14:46:41

A siren placed at a railway platfrom is emitting sound of frequency 5 kHz. A passenger sitting in a moving train A records a frequency of 5.5 kHz while the train approaches the siren. During his return journey in a different train B he records a frequency of 6.0 kHz while approaching the same siren. The ratio of velocity of train B to that of train A is

1.242 / 252

2.2

3.5 / 6

4.11 / 6

**Posted Date**:-2021-12-23 15:33:19

A surface at temperature T0Â°K receives power P by radiation from a small sphere at temperature T >> T0 and at a distance d. if both T and d are doubled, the power received by surface will becomes approximately

1.P

2.2p

3. 4p

4.16p

**Posted Date**:-2021-12-23 14:21:39

Absorptive power of perfectly black body is

1.Zero

2.Infinity

3.One

4.Constant

**Posted Date**:-2021-12-23 14:07:43

According to kinetic theory of gases, at absolute zero of temperature

1.Water freezes

2.Liquid helium freezes

3.Molecular motion stops

4.Liquid hydrogen freezes

**Posted Date**:-2021-12-23 14:59:44

An engine has an efficiency of 1/6. When the temperature of sink is reduced by 62Â°C, its efficiency is doubled. Temperature of the source is:

1.124Â°C

2.37Â°C

3.62Â°C

4.99Â°C

**Posted Date**:-2021-12-23 14:28:06

An ideal gas is that which can

1.Be solidified

2.Liquefied

3.Not be liquefied

4.Not be solidified

**Posted Date**:-2021-12-23 14:52:04

An observer is moving towards a stationary source of frequency 250 Hz with a velocity of 40 m/s. If the velocity of sound is 330 m/s, the apparent frequency heard by the observer will be

1.320 Hz

2. 300 Hz

3.280 Hz

4. 260 Hz

**Posted Date**:-2021-12-23 15:29:41

At a certain temperature, hydrogen molecules have r.m.s. velocity of 3 km/s. what is the r.m.s velocity of the oxygen molecules at the same temperature?

1.0.25 km/s

2.0.5 km/s

3.0.75 km/s

4.6 km/s

**Posted Date**:-2021-12-23 14:49:32

At a given volume and temperature, the pressure of a gas

1.varies inversely as its mass

2. varies inversely as the square of its mass

3. varies linearly as its mass

4.is independent of its mass

**Posted Date**:-2021-12-23 14:30:17

Average kinetic energy of molecules is

1.Directly proportional to square root of temperature

2.Directly proportional to absolute temperature

3.Independent of absolute temperature

4.Inversely proportional to absolute temperature

**Posted Date**:-2021-12-23 14:56:41

Co-efficient of reflection, coefficient of absorption and coefficient transmission are related as

1.a + r + 1 = 1

2.a + r + t1 1

3.a + r = -t

4.a1 r + 1

**Posted Date**:-2021-12-23 14:24:54

Directions: The following question has four choices out of which ONLY ONE is correct. A Carnots engine works as a refrigerator between 250 K and 300 K. If it receives 750 calories of heat from the reservoir at the lower temperature, the amount of heat rejected at the higher temperature is __________.

1. 900 cal

2. 625 cal

3.750 cal

4.1000 cal

**Posted Date**:-2021-12-23 14:33:14

Directions: The following question has four choices out of which ONLY ONE is correct. A thermodynamical system is changed from state (P1, V1) to (PÂ², VÂ²) by two different processes, the quantity which will remain same is:

1.Î”Q

2.Î”W

3.Î”Q + Î”W

4. Î”Q â€“ Î”W

**Posted Date**:-2021-12-23 14:26:46

Directions: The following question has four choices out of which ONLY ONE is correct. In a thermodynamic process, pressure of a fixed mass of the gas is changed in such a manner that the gas molecules give out 30 J of heat. Also, 10 J of work is done on the gas. If the internal energy of the gas was 40 J, what will be the final internal energy?

1.20 J

2.-20 J

3. 80 J

4.zero

**Posted Date**:-2021-12-23 14:31:11

Directions: The following question has four choices out of which ONLY ONE is correct. Which of the following is incorrect regarding the first law of thermodynamics? A. It is not applicable to any cyclic process B. It is a restatement of the principle of conservation of energy C. It introduces the concept of the internal energy D. It introduces the concept of the entropy

1. A and D

2.B and C

3.C and A

4. A and B

**Posted Date**:-2021-12-23 14:29:24

During an adiabatic process, the pressure of a gas is found to be proportional to the cube of its absolute temperature. The ratio Cp/Cv for the gas is

1. 2

2. 3/2

3. 4/3

4. 5/3

**Posted Date**:-2021-12-23 14:37:27

Emissivity of perfectly black body is

1.1

2.2

3.5

4.0

**Posted Date**:-2021-12-23 14:22:58

Energy is not carried by

1.Longitudinal progressive waves

2. Electromagnetic waves

3.Transverse progressive waves

4.Stationary wave

**Posted Date**:-2021-12-23 15:34:03

Energy supplied to convert unit mass of substance from solid to liquid state at its melting point is called

1.Latent heat of fusion

2.Evaporation

3.Solidification

4.Latent heat of fission

**Posted Date**:-2021-12-23 14:50:51

Following gases are kept at the same temperature. Which gas possesses maximum r.m.s. speed?

1.Oxygen

2.Nitrogen

3.Hydrogen

4.Carbon dioxide

**Posted Date**:-2021-12-23 14:58:49

For a diatomic gas change in internal energy for a unit change in temperature for constant pressure and constant volume is U1 and U2 respectively. What is the ratio of U1 and U2?

1.5 : 3

2.3 : 5

3. 1 : 1

4.5 : 7

**Posted Date**:-2021-12-23 14:35:09

For a diatomic gas change in internal energy for a unit change in temperature for constant pressure and constant volume is U1 and U2 respectively. What is the ratio of U1 and U2?

1.5 : 3

2.3 : 5

3. 1 : 1

4.5 : 7

**Posted Date**:-2021-12-23 14:35:27

For a gas, the r.m.s. speed at 800K is

1. Half the value at 200 K

2.Double the value at 200 K

3.Same as at 200 K

4.Four times the value at 200 K

**Posted Date**:-2021-12-23 14:54:47

For a magnet of time period T magnetic moment is M, if the magnetic moment becomes one fourth of the initial value, then the time period of oscillation becomes.

1.Half of initial value

2.One fourth of initial value

3.Double of initial value

4.Four time initial value

**Posted Date**:-2021-12-23 15:12:50

For which of the following process, the thermal conduction is maximum?

1.Combustion

2.Radiation

3.Convection

4.Conduction

**Posted Date**:-2021-12-23 14:09:57

Heat cannot by itself flow from a body at lower temperature to a body at higher temperature is a statement as a conseqence of

1.conservation of mass

2.conservation of momentum

3.first law of thermodynamics

4.second law of thermodynamics

**Posted Date**:-2021-12-23 14:36:21

If 2 kcal, of heat is supplied to a system cause to change the internal energy of a gas is 5030 J, and external work done is 3350 J, then what is mechanical equivalent of heat?

1. 41.90 J/kcal

2.4190 J/cal

3.4.19 J/kcal

4.4.19 J/cal

**Posted Date**:-2021-12-23 14:53:47

If a hole is bored along the diameter of the earth and a stone is dropped into the hole

1.The stone reaches the centre of the earth and stops there

2.The stone reaches the other side of the earth and stops there

3. The stone executes simple harmonic motion about the centre of the earth

4.The stone reaches the other side of the earth and escapes into space

**Posted Date**:-2021-12-23 15:26:36

If a simple harmonic oscillator has got a displacement of 0.02 m and acceleration equal to 2.0 ms-2 at any time, the angular frequency of the oscillator is equal to

1.10 rad s-1

2. 1 rad s-1

3.100 rad s-1

4. 1 rad s-1

**Posted Date**:-2021-12-23 15:21:27

If the length of seconds pendulum is increased by 2%, how may seconds it will lose per day?

1. 3427 sec

2.3727 sec

3.3927 sec

4. 864 sec

**Posted Date**:-2021-12-23 15:20:03

In damped oscilation the directions of the restoring force and the resistive force

1.are the same

2.are opposite

3.may be same or opposite

4.have no relation with each other

**Posted Date**:-2021-12-23 15:08:42

In damped oscilation, the angular frequency of the oscillator

1. keeps on decreasing

2.keeps on increasing

3.emains the same

4. fluctuates

**Posted Date**:-2021-12-23 15:17:01

In SHM, graph of which of the following is a straight line?

1.T.E. against displacement

2.P.E. against displacement

3.Acceleration against time

4.Velocity against displacement

**Posted Date**:-2021-12-23 15:18:38

In the case of forced oscillations, which of the following statements is not true?

1.frequency equals that of external periodic force

2.amplitude depends upon the damping coefficient

3.amplitude tends to infinity at resonance

4.higher the damping coefficient, lower is the amplitude at resonance

**Posted Date**:-2021-12-23 15:14:51

Latent heat of ice is

1.Less than external latent heat of fusion

2.Equal to external latent heat of fusion

3.More then external latent heat of fusion

4. Twice the external latent heat of fusion

**Posted Date**:-2021-12-23 14:50:17

Length of a simple pendulum executing simple harmonic motion is increased by 21%. The percentage increase in the time â€“ period of the pendulum of increased length is

1.10%

2.1%

3.21%

4.42%

**Posted Date**:-2021-12-23 15:20:48

Loudness of a note of sound is

1.Directly proportional to amplitude of the wave

2.Directly proportional to square of amplitude of wave

3.Directly proportional to velocity of the wave

4.Directly proportional to square of velocity of the wave

**Posted Date**:-2021-12-23 15:31:16

Moon has no atmosphere because

1.It is far away form the surface of the earth

2.Its surface temperature is 10Â°C

3.The r.m.s. velocity of all the gas molecules is more then the escape velocity of the moons surface

4.The escape velocity of the moons surface is more than the r.m.s velocity of all molecules

**Posted Date**:-2021-12-23 14:48:38

One mole of an ideal gas requires 207 J heat to raise the temperature by 10 K, when heated at constant pressure. If the same gas is heated at constant volume to raise the temperature by 10K, then heat required is

1. 96.6 J

2.124 J

3.198.8 J

4.215.4 J

**Posted Date**:-2021-12-23 14:53:07

One mole of mono atomic gas (g = 5/3) is mixed with one mole of diatomic gas (g = 7/5) what will be the value of g for the mixture?

1.1.5

2.2.5

3.1.0

4.2

**Posted Date**:-2021-12-23 14:46:09

one of the two clocks on the earth is controlled by a pendulum and other by a spring. If both the clocks are taken to the moon, then which clock will have the same time â€“ period of the earth?

1.spring clock

2.pendulum clock

3.both

4.None

**Posted Date**:-2021-12-23 15:11:15

Real gases show mark able deviation from that of ideal gas behavior at

1.High temperature and low pressure

2.Low temperature and high pressure

3.High temperature and high pressure

4.Low temperature and low pressure

**Posted Date**:-2021-12-23 14:45:23

Spring is pulled down by 2 cm. What is amplitude of motion?

1. 0 cm

2.6 cm

3. 2 cm

4.cm

**Posted Date**:-2021-12-23 15:10:06

The acceleration of particle executing S.H.M. when it is at mean position is

1.Infinite

2.Varies

3.Maximum

4.Zero

**Posted Date**:-2021-12-23 15:17:41

The average kinetic energy of the molecules of a gas at 27Â°C is 9 10-20 J. what is its average K.E. at 227Â°C?

1. 5 10-20 J

2.10 10-20 J

3.15 10-20 J

4.20 10-20 J

**Posted Date**:-2021-12-23 15:00:48

The best ideal black body is

1. Lamp of charcoal heated to high temperature

2.Metal coated with a black dye

3.Glass surface coated with coalter

4.Hollow enclosure blackened inside and having a small hole

**Posted Date**:-2021-12-23 14:14:46

The bob of a simple pendulum is a spherical hollow ball filled with water. A plugged hall near the bottom of the oscillating bob gets suddenly unplugged. During observation, till water is coming out, the time -period of the oscillation would

1.first decrease and then increase to the original value

2.first increase and then decrease to the original value

3.increase towards a saturation value

4. remain unchanged

**Posted Date**:-2021-12-23 15:22:24

The displacement y of a particle executing periodic motion is given by y = 4 cosÂ² (t/2) sin (1000t). This expression may be considered to be a result of superposition of the following number of harmonic motions

1. two

2.three

3.four

4.five

**Posted Date**:-2021-12-23 15:09:28

The earth intercepts approximately one billionth of the power radiated by the sun. if the surface temperature of the sun were to drop by a factor of 2, the average radiant energy incident on earth per second would reduce by factor of

1.2

2.4

3.8

4.16

**Posted Date**:-2021-12-23 14:15:38

The earth receives at its surface radiation from the sun at the rate of 1400 W/mÂ². the distance of the centre of the sun from the surface of the earth is 1.5 1011 m and the radius of the sun is 7.0 108 m. treating sun as a black body, it follows from the above data that its surface temperature is,

1.5801 K

2.106 K

3. 50.1 K

4. 2801 C

**Posted Date**:-2021-12-23 14:20:43

The frequency of the note produced by plucking a given string increases as

1. The length of the string increases

2.The tension in the string increases

3.The tension in the string decreases

4.The mass per unit length of the string increases

**Posted Date**:-2021-12-23 15:32:28

The good absorber of heat are

1.Non-emitter

2.Poor-emitter

3.Good-emitter

4.Highly polished

**Posted Date**:-2021-12-23 14:11:25

The maximum velocity for particle in SHM is 0.16 m/s and maximum acceleration is 0.64 m/s2. The amplitude is

1.4 Ã— 10-2 m

2.4 Ã— 10-1 m

3.4 Ã— 10 m

4. 4 Ã— 100 m

**Posted Date**:-2021-12-23 15:25:03

The motion of a particle executing simple harmonic motion is given by X = 0.01 sin 100p (t + 0.05), where X is in metres ant t in second. The time period in second is

1. 0.001

2.0.02

3. 0.1

4.0.2

**Posted Date**:-2021-12-23 15:15:34

The period of a simple harmonic oscillator is 2 sec. The ratio of its maximum velocity and maximum acceleration is

1.âˆ

2.1/âˆ

3. 2âˆ

4.4

**Posted Date**:-2021-12-23 15:25:46

The period of thin magnet is 4 sec. if it is divided into two equal halves then the time period of each part will be

1.4 sec

2. 1 sec

3.2 sec

4.8 sec

**Posted Date**:-2021-12-23 15:19:21

The process of heat transfer in which heat is transferred with actual migration of medium particles is known as (AFMC-94)

1.Conduction

2.Convection

3.Radiation

4.Reflection

**Posted Date**:-2021-12-23 14:16:14

The specific heat of a gas

1.Has only one value

2.Has two values CP and CV

3. Is proportional to the square root of its absolute temperature

4. Can have any value between 0 and infinity

**Posted Date**:-2021-12-23 14:55:48

The temperature at which the r.m.s. velocity of HÂ² becomes escape velocity from the earth is,

1.10059Â°C

2.10059 K

3.10332Â°C

4.10332 K

**Posted Date**:-2021-12-23 14:47:30

The temperature of a gas is -68Â°C. to what temperature should it be heated, so that the r.m.s. velocity of the molecules be doubled?

1. 357Â°C

2. 457Â°C

3.547Â°C

4.820Â°C

**Posted Date**:-2021-12-23 14:58:01

The temperature of a piece of metal is raised from 27Â°C to 51.2Â°C. the rate at which metal radiates energy increases nearly

1.1.36 times

2.2.36 times

3. 3.36 times

4.4.36 times

**Posted Date**:-2021-12-23 14:22:24

The temperatures of inside and outside of a refrigerator are 273 K and 303 K respectively. Assuming, that the refrigerator cycle is reversible, for every joule of work done, the heat delivered to the surrounding will be nearly:

1.10 J

2.20 J

3.30 J

4.50 J

**Posted Date**:-2021-12-23 14:27:28

The translational kinetic energy of gas molecules at temperature T for one mole of a gas is

1. (3/2) RT

2.(9/2) RT

3.(1/3) RT

4.(5/2) RT

**Posted Date**:-2021-12-23 14:31:59

Time period of simple pendulum of length l and a place where acceleration due to gravity is g is T. what is the period of a simple pendulum of the same length at a place where the acceleration due to gravity is 1.029 is,

1.T

2.1.02 T

3.0.99 T

4.1.01 T

**Posted Date**:-2021-12-23 15:13:32

Two stars A and B radiate maximum energy at 3600Â°A and 3600Â°A respectively. Then the ratio of absolute temperatures of A and B is

1.256 : 81

2.81 : 256

3. 3 : 4

4. 4 : 3

**Posted Date**:-2021-12-23 14:12:01

Unit of Stefans constant is given by

1. W/ m KÂ²

2.W/ mÂ² KÂ²

3.WÂ²/ mÂ² K4

4.W/ mK

**Posted Date**:-2021-12-23 14:17:03

When a particle performing uniform circular motion of radius 10 cm undergoes the SHM, what will be its amplitude?

1.10 cm

2.5 cm

3.2.5 cm

4. 20 cm

**Posted Date**:-2021-12-23 15:12:04

Which of the following is the unit of specific

1.J kg/Â°c

2.J/kgÂ°c

3. kgÂ°c/J

4. J kg/Â°cÂ²

**Posted Date**:-2021-12-23 14:51:26

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

1. work

2.volume

3.pressure

4.Temperature

**Posted Date**:-2021-12-23 14:32:36

With the increase in temperature, the frequency of the sound from an organ pipe

1.Decreases

2.Increases

3.Remain unchanged

4.Changes erratically

**Posted Date**:-2021-12-23 15:30:25

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