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PHXI12:THERMODYNAMICS

371315 For a given heat engine,
I.
Efficiency can be 1 .
II.
Conversion of heat into work can be done by heating the system by an external furnace, as in a steam engine.
Choose the incorrect statement.

1 Only I

2 Only II

3 Neither I nor II

4 Both I and II

Explanation:

Efficiency of a heat engine,
$η = 1 - \frac{Q_{2}}{Q_{1}}$
When $Q_{2} = 0$ , then $η = 1$ .
However in practice, $η = 1$ is never possible even if we can eliminate various kinds of losses associated with actual heat engines.
So, option (1) is correct.

PHXI12:THERMODYNAMICS

371316 An engine takes compressed steam at $127^{\circ} C$ and rejects it at $47^{\circ} C$ . Efficiency of the engine is

1

35 %

2

60 %

3

40 %

4

20 %

Explanation:

As,
$η = 1 - \frac{T_{2}}{T_{1}} = 1 - \frac{(47 + 273)}{(127 + 273)} = 1 - \frac{320}{400} = \frac{1}{5} = 20 %$

PHXI12:THERMODYNAMICS

371317 The heat engine would operate by taking heat at a particular temperature and

1 Converting it all into work

2 Converting some of it into work and rejecting the rest at lower temperature

3 Converting some of it into work and rejecting the rest at same temperature

4 Converting some of it into work and rejecting the rest at a higher temperature .

PHXI12:THERMODYNAMICS

371318 If the efficiency of an engine is $50 %$ and its work output is $500 J,$ then find the value of input work.

1

1000 J

2

500 J

3

100 J

4

250 J

Explanation:

$∵$ Efficiency of heat engine is
$η = \frac{Work done}{Heat input} \times 100$
or $\frac{η}{100} = \frac{Work done}{Heat input} = \frac{500}{Heat input}$
Heat input $= \frac{500 \times 100}{50} = 1000 J$

PHXI12:THERMODYNAMICS

371319 The efficiency of a heat engine:

1 Is independent of the temperature of the source and the sink

2 is independent of the working substance

3 can be

100 %

4 is not affected by the thermal capacity of the source or the sink

PHXI12:THERMODYNAMICS

371315 For a given heat engine,
I.
Efficiency can be 1 .
II.
Conversion of heat into work can be done by heating the system by an external furnace, as in a steam engine.
Choose the incorrect statement.

1 Only I

2 Only II

3 Neither I nor II

4 Both I and II

Explanation:

Efficiency of a heat engine,
$η = 1 - \frac{Q_{2}}{Q_{1}}$
When $Q_{2} = 0$ , then $η = 1$ .
However in practice, $η = 1$ is never possible even if we can eliminate various kinds of losses associated with actual heat engines.
So, option (1) is correct.

PHXI12:THERMODYNAMICS

371316 An engine takes compressed steam at $127^{\circ} C$ and rejects it at $47^{\circ} C$ . Efficiency of the engine is

1

35 %

2

60 %

3

40 %

4

20 %

Explanation:

As,
$η = 1 - \frac{T_{2}}{T_{1}} = 1 - \frac{(47 + 273)}{(127 + 273)} = 1 - \frac{320}{400} = \frac{1}{5} = 20 %$

PHXI12:THERMODYNAMICS

371317 The heat engine would operate by taking heat at a particular temperature and

1 Converting it all into work

2 Converting some of it into work and rejecting the rest at lower temperature

3 Converting some of it into work and rejecting the rest at same temperature

4 Converting some of it into work and rejecting the rest at a higher temperature .

PHXI12:THERMODYNAMICS

371318 If the efficiency of an engine is $50 %$ and its work output is $500 J,$ then find the value of input work.

1

1000 J

2

500 J

3

100 J

4

250 J

Explanation:

$∵$ Efficiency of heat engine is
$η = \frac{Work done}{Heat input} \times 100$
or $\frac{η}{100} = \frac{Work done}{Heat input} = \frac{500}{Heat input}$
Heat input $= \frac{500 \times 100}{50} = 1000 J$

PHXI12:THERMODYNAMICS

371319 The efficiency of a heat engine:

1 Is independent of the temperature of the source and the sink

2 is independent of the working substance

3 can be

100 %

4 is not affected by the thermal capacity of the source or the sink

PHXI12:THERMODYNAMICS

371315 For a given heat engine,
I.
Efficiency can be 1 .
II.
Conversion of heat into work can be done by heating the system by an external furnace, as in a steam engine.
Choose the incorrect statement.

1 Only I

2 Only II

3 Neither I nor II

4 Both I and II

Explanation:

Efficiency of a heat engine,
$η = 1 - \frac{Q_{2}}{Q_{1}}$
When $Q_{2} = 0$ , then $η = 1$ .
However in practice, $η = 1$ is never possible even if we can eliminate various kinds of losses associated with actual heat engines.
So, option (1) is correct.

PHXI12:THERMODYNAMICS

371316 An engine takes compressed steam at $127^{\circ} C$ and rejects it at $47^{\circ} C$ . Efficiency of the engine is

1

35 %

2

60 %

3

40 %

4

20 %

Explanation:

As,
$η = 1 - \frac{T_{2}}{T_{1}} = 1 - \frac{(47 + 273)}{(127 + 273)} = 1 - \frac{320}{400} = \frac{1}{5} = 20 %$

PHXI12:THERMODYNAMICS

371317 The heat engine would operate by taking heat at a particular temperature and

1 Converting it all into work

2 Converting some of it into work and rejecting the rest at lower temperature

3 Converting some of it into work and rejecting the rest at same temperature

4 Converting some of it into work and rejecting the rest at a higher temperature .

PHXI12:THERMODYNAMICS

371318 If the efficiency of an engine is $50 %$ and its work output is $500 J,$ then find the value of input work.

1

1000 J

2

500 J

3

100 J

4

250 J

Explanation:

$∵$ Efficiency of heat engine is
$η = \frac{Work done}{Heat input} \times 100$
or $\frac{η}{100} = \frac{Work done}{Heat input} = \frac{500}{Heat input}$
Heat input $= \frac{500 \times 100}{50} = 1000 J$

PHXI12:THERMODYNAMICS

371319 The efficiency of a heat engine:

1 Is independent of the temperature of the source and the sink

2 is independent of the working substance

3 can be

100 %

4 is not affected by the thermal capacity of the source or the sink

PHXI12:THERMODYNAMICS

371315 For a given heat engine,
I.
Efficiency can be 1 .
II.
Conversion of heat into work can be done by heating the system by an external furnace, as in a steam engine.
Choose the incorrect statement.

1 Only I

2 Only II

3 Neither I nor II

4 Both I and II

Explanation:

Efficiency of a heat engine,
$η = 1 - \frac{Q_{2}}{Q_{1}}$
When $Q_{2} = 0$ , then $η = 1$ .
However in practice, $η = 1$ is never possible even if we can eliminate various kinds of losses associated with actual heat engines.
So, option (1) is correct.

PHXI12:THERMODYNAMICS

371316 An engine takes compressed steam at $127^{\circ} C$ and rejects it at $47^{\circ} C$ . Efficiency of the engine is

1

35 %

2

60 %

3

40 %

4

20 %

Explanation:

As,
$η = 1 - \frac{T_{2}}{T_{1}} = 1 - \frac{(47 + 273)}{(127 + 273)} = 1 - \frac{320}{400} = \frac{1}{5} = 20 %$

PHXI12:THERMODYNAMICS

371317 The heat engine would operate by taking heat at a particular temperature and

1 Converting it all into work

2 Converting some of it into work and rejecting the rest at lower temperature

3 Converting some of it into work and rejecting the rest at same temperature

4 Converting some of it into work and rejecting the rest at a higher temperature .

PHXI12:THERMODYNAMICS

371318 If the efficiency of an engine is $50 %$ and its work output is $500 J,$ then find the value of input work.

1

1000 J

2

500 J

3

100 J

4

250 J

Explanation:

$∵$ Efficiency of heat engine is
$η = \frac{Work done}{Heat input} \times 100$
or $\frac{η}{100} = \frac{Work done}{Heat input} = \frac{500}{Heat input}$
Heat input $= \frac{500 \times 100}{50} = 1000 J$

PHXI12:THERMODYNAMICS

371319 The efficiency of a heat engine:

1 Is independent of the temperature of the source and the sink

2 is independent of the working substance

3 can be

100 %

4 is not affected by the thermal capacity of the source or the sink

PHXI12:THERMODYNAMICS

371315 For a given heat engine,
I.
Efficiency can be 1 .
II.
Conversion of heat into work can be done by heating the system by an external furnace, as in a steam engine.
Choose the incorrect statement.

1 Only I

2 Only II

3 Neither I nor II

4 Both I and II

Explanation:

Efficiency of a heat engine,
$η = 1 - \frac{Q_{2}}{Q_{1}}$
When $Q_{2} = 0$ , then $η = 1$ .
However in practice, $η = 1$ is never possible even if we can eliminate various kinds of losses associated with actual heat engines.
So, option (1) is correct.

PHXI12:THERMODYNAMICS

371316 An engine takes compressed steam at $127^{\circ} C$ and rejects it at $47^{\circ} C$ . Efficiency of the engine is

1

35 %

2

60 %

3

40 %

4

20 %

Explanation:

As,
$η = 1 - \frac{T_{2}}{T_{1}} = 1 - \frac{(47 + 273)}{(127 + 273)} = 1 - \frac{320}{400} = \frac{1}{5} = 20 %$

PHXI12:THERMODYNAMICS

371317 The heat engine would operate by taking heat at a particular temperature and

1 Converting it all into work

2 Converting some of it into work and rejecting the rest at lower temperature

3 Converting some of it into work and rejecting the rest at same temperature

4 Converting some of it into work and rejecting the rest at a higher temperature .

PHXI12:THERMODYNAMICS

371318 If the efficiency of an engine is $50 %$ and its work output is $500 J,$ then find the value of input work.

1

1000 J

2

500 J

3

100 J

4

250 J

Explanation:

$∵$ Efficiency of heat engine is
$η = \frac{Work done}{Heat input} \times 100$
or $\frac{η}{100} = \frac{Work done}{Heat input} = \frac{500}{Heat input}$
Heat input $= \frac{500 \times 100}{50} = 1000 J$

PHXI12:THERMODYNAMICS

371319 The efficiency of a heat engine:

1 Is independent of the temperature of the source and the sink

2 is independent of the working substance

3 can be

100 %

4 is not affected by the thermal capacity of the source or the sink