Thermodynamics Test

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Thermodynamics Test - 68

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Weekly Quiz Competition

Question 1
1 / -0

In changing the state of thermodynamics from A to B state, the heat required is Q and the work done by the system is W. The change in its internal energy is

A
Q + W

B
Q - W

C
Q

D
$$d{Q - W}{2}$$

Solution

From the first law of thermodynamics
$$\Delta Q=\Delta U+\Delta W $$
$$W=+ve, Q=+ve$$
$$ \Rightarrow \Delta U =\Delta Q - \Delta W $$
Question 2
1 / -0

First law of thermnodynamics is given by

A
dq = du + pdv

B
dQ = dU $$\times $$ Pdv

C
dQ = (dU + dV) P

D
dQ = PdU + dV

Solution

The first law of thermodynamics is given as $$\Delta Q=\Delta U+\Delta W $$ and $$\Delta W = P\Delta V $$, where $$\Delta U$$ is the change in internal energy of a system, $$Q$$ is the net heat transfer (the sum of all heat transfer into and out of the system), and $$W$$ is the net work done (the sum of all work done on or by the system)
Question 3
1 / -0

The first law of thermodynamics is concerned with the conservation of

A
Momentum

B
Energy

C
Mass

D
Temperature

Solution

The First Law of Thermodynamics states that heat is a form of energy, and thermodynamic processes are therefore subject to the principle of conservation of energy. This means that heat energy cannot be created or destroyed
Question 4
1 / -0

A system perform work $$\bigtriangleup W$$ when an amount of heat $$\bigtriangleup Q$$ added to the system the corresponding change in the internal energy is $$\bigtriangleup U$$. A unique function of the intial and final states (irrespective of the mode of change ) is

A
$$\bigtriangleup Q$$

B
$$\bigtriangleup W$$

C
$$\bigtriangleup U$$ and $$\bigtriangleup Q$$

D
$$\bigtriangleup U$$

Solution

Change in internal energy $$ \left ( \Delta U \right ) $$ depends upon initial an find state of the function while $$ \Delta Q $$ and $$ \Delta W $$ are path depends also.
Question 5
1 / -0

If the amount of heat given to a system be 35 joules and the amount of work done by the system be - 15 joules, then the change in the internal energy of the system is

A
-500 Joules

B
20 Joules

C
30 Joules

D
50 Joules

Solution

From the first law of thermodynamics.
$$Q=+ve $$ because heat is given to the system and $$W=-ve$$ because work done is by the system.
$$ \Delta Q = \Delta W +\Delta U\Rightarrow 35 = -15+\Delta U\Rightarrow \Delta U = 50 J $$
Question 6
1 / -0

For an idea gas, in an isothermal process

A
Heat content remains constant

B
Heat content and temperature remain constant

C
Temperature remain constant

D
None of the above

Solution

An isothermal process is a change of a system, in which the temperature remains constant
Question 7
1 / -0

In an isothermal expansion

A
Internal energy of the gas increases

B
Internal energy of the gas decreases

C
Internal energy remains unchanged

D
Average kinetic energy of gas molecule decreases

Solution

In isothermal expansion temperature remains constant, hence no change in internal energy.
Question 8
1 / -0

In isothermic process, which statement is wrong

A
Temperature is constant

B
Internal energy is constant

C
No exchange of energy

D
(a) and (b) are correct

Solution

In isothermal process, exchange of energy takes place between system and surrounding to maintain the system temperature constant.
Question 9
1 / -0

In a thermodynamic process, pressure of a fixed mass of a gas is changed in such a manner that the gas molecules given out $$30$$ J of heat and $$10$$ J of work is done on the gas. If the initial internal energy of the gas was $$40$$ J. Then the final internal energy will be

A
$$30$$ J

B
$$20$$ J

C
$$60$$ J

D
$$40$$ J

Solution

From the first law of Thermodynamics
$$ \Delta Q=\Delta U+\Delta W = \left ( U_{f}-U_{f} \right )+\Delta W $$
$$\Rightarrow 30=\left ( U_{f}-40 \right ) + 10\Rightarrow U_{f}= 60J $$
Question 10
1 / -0

A thermally container is divided into two parts by a screen. In one part the pressure and temperature are P and t for an idea gas filled. In the second part it is vaccum. If mow a small hole is created in the screen, then the temperature of the gas will

A
Decrease

B
Increase

C
Remain same

D
None of the above

Solution

This is the case of free expansion of gas. In free expansion $$\Delta U=0\Rightarrow $$ Temp. remains same.

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Re-Attempt Weekly Quiz Competition

Thermodynamics Test - 68

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Thermodynamics Test - 68

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SHARING IS CARING

Question 1

Q + W

Q - W

Q

$$d{Q - W}{2}$$

Solution

Question 2

dq = du + pdv

dQ = dU $$\times $$ Pdv

dQ = (dU + dV) P

dQ = PdU + dV

Solution

Question 3

Momentum

Energy

Mass

Temperature

Solution

Question 4

$$\bigtriangleup Q$$

$$\bigtriangleup W$$

$$\bigtriangleup U$$ and $$\bigtriangleup Q$$

$$\bigtriangleup U$$

Solution

Question 5

-500 Joules

20 Joules

30 Joules

50 Joules

Solution

Question 6

Heat content remains constant

Heat content and temperature remain constant

Temperature remain constant

None of the above

Solution

Question 7

Internal energy of the gas increases

Internal energy of the gas decreases

Internal energy remains unchanged

Average kinetic energy of gas molecule decreases

Solution

Question 8

Temperature is constant

Internal energy is constant

No exchange of energy

(a) and (b) are correct

Solution

Question 9

$$30$$ J

$$20$$ J

$$60$$ J

$$40$$ J

Solution

Question 10

Decrease

Increase

Remain same

None of the above

Solution

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