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Thermal equilibrium - class-IX

Description: thermal equilibrium
Number of Questions: 16
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Tags: heat and thermodynamics physics thermal physics heat and energy
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Two bodies A and B are said to be in thermal equilibrium with each other, if :

  1. heat flows from A to B

  2. heat flows from B to A

  3. both the bodies lose equal amounts of heat to the atmosphere

  4. heat does not flow from either A or B


Correct Option: D
Explanation:

The correct answer is option(D).

Thermal equivalence happens when there is no temperature difference between two bodies. And no heat transfer happens.

For 2 gases in thermal equilibrium with each other , Pressure of the gases 

  1. varies as speed of the gas molecules

  2. varies as square root of the gas molecules

  3. varies inversely as the gas molecules

  4. remains same


Correct Option: D
Explanation:

For the ideal gas equation $PV=nRT$

if T is constant the pressure is also constant
hence  when the gases in thermal equilibrium have same temperature their pressure remains same .
 hence option D is correct.

Two systems are in thermal equilibrium. The quantity which is common for them is

  1. heat

  2. momentum

  3. specific heat

  4. temperature


Correct Option: D
Explanation:

Thermal equilibrium implies that there is no heat transfer taking place between the given two bodies i.e. there temperature is same.

When a gas  is in thermal equilibrium, its molecules

  1. have the same average kinetic energy.

  2. have different energies which remains constant.

  3. have a certain constant energy.

  4. do not collide with one another.


Correct Option: A
Explanation:

When a gas is in thermal equilibrium, the temperature throughout the gas is the same. (Zeroth law of thermodynamics)
The average kinetic energy of the gas molecules is directly proportional to the absolute temperature of the gas. I.e. different sections of the gas will all have the same average kinetic energy.

Two metal spheres of different radii having same temperature are placed in thermal contact in a vaccum. Which of the following quantities is certainly correct?

  1. Each sphere has the same internal energy

  2. There is no net transfer of thermal energy between the spheres

  3. Both spheres radiate electromagnetic energy at the same rate

  4. The larger sphere a greater mean internal energy per atom than the smaller sphere


Correct Option: B
Explanation:

There is no net transfer of thermal energy between the spheres.

Option B is correct.

Two bodies are in thermal equilibrium if they have same

  1. temperature

  2. amount of heat

  3. specific heat

  4. thermal capacity


Correct Option: A
Explanation:

Thermal equilibrium means that there is no heat transfer going on between the bodies, which simply means that the bodies are at the same temperature. Heat content is a whole different concept - it is the amount of heat contained in a body, which is crucially dependent on mass. 

Two bodies A and B are said to be in thermal equilibrium with each other, if

  1. heat flows from A to B

  2. heat flows from B to A

  3. both the bodies lose equal amunts of heat to the atmosphere

  4. heat does not flow from either A or B


Correct Option: D
Explanation:

Two bodies A and B are said to be in thermal equilibrium with each other, ifheat does not flow from either A or B 

Two systems in thermal equilibrium with a third system separately are in thermal equilibrium with each other.
The above statement is

  1. First law of thermodynamics

  2. Second law of thermodynamics

  3. Third law of thermodynamics

  4. Zeroth law of thermodynamics


Correct Option: D
Explanation:

The given statement is the exact statement of Zeroth law of thermodynamics which deals with thermal equilibrium.

Three bodies $A, B$ and $C$ are in thermal equilibrium.
The temperature of $B$ is $45^{\circ}C$. Then the temperature of $'C'$ is _____

  1. $45^{\circ}C$

  2. $50^{\circ}C$

  3. $40^{\circ}C$

  4. Any temperature


Correct Option: A
Explanation:

A, B and C are in thermal equilibrium and B is at temperature $45^0 C$, then according to zeroth law of thermodynamics both A and C will also be at temperature $45^0 C$.

If the output energy is$ 1000 J$ and input energy is $200 J $the net output is _____ $J$.

  1. $800$

  2. $1200$

  3. $10$

  4. $500$


Correct Option: A
Explanation:

The net output $=$ output - input
$= 1000 - 200 = 800 J$

In thermal equilibrium concepts, heat lost by hot body is equal to

  1. Heat gained by hot body

  2. Heat gained by cold body

  3. Both (a) and (b)

  4. None of these


Correct Option: B
Explanation:

It is very clear that heat flows from hot body to cold body under general conditions. 

So (B) is the correct option. 

The variance defined by Zeroth law of thermodynamics is

  1. Temperature

  2. Internal energy

  3. Work

  4. All of these


Correct Option: A

Four cubes of ice at $-10^{o}C$ each one gm is taken out from the refrigerator and are put in $150\ gm$ of water at $20^{o} C$. The temperature of water when thermal equilibrium is attained. Assume that no heat is lost to the outside and water equivalent of container is $46\ gm$. (Specific heat capacity of water $=1\ cal/gm-\ ^{o}C$, Specific heat capacity of fusion of ice $=0.5 cal/gm-\ ^{o}C$, Latent heat of fusion of ice $= 80\ cal/gm$)

  1. $0^{o}C$

  2. $-10^{o}C$

  3. $17.9^{o}C$

  4. $None$


Correct Option: A

$1\ g$ of ice is mixed with $1\ g$ of steam. At thermal equilibrium, the temperature of the mixture is

  1. $50^{\circ}C$

  2. $0^{\circ}C$

  3. $55^{\circ}C$

  4. $100^{\circ}C$


Correct Option: D

Two bodies are said to be in the state of thermal equilibrium if there is no transfer of heat taking place between them. True or false.

  1. True

  2. False


Correct Option: A
Explanation:
Thermal equilibrium is said to be achieved when there is no exchange of heat in the system.
Hence, OPTION : A (true).

According to Hess's law, the thermal effects of a reaction depends on

  1. Initial and final conditions of the reacting substances

  2. Initial concentration of reactants

  3. Final conditions of the reacting substances

  4. Not on initial and final conditions of the reacting substance


Correct Option: A
Explanation:

According to Hess law, the thermal effects of a reaction depends upon the initial and final conditions of the reacting substances. It does not depend upon the immediate steps.

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