Test: First Law of Thermodynamics

QUESTION: 1

The first law of thermodynamics is the law of

A.
conservation of mass
B.
conservation of energy
C.
conservation of momentum
D.
conservation of temperature

Solution:

The First Law of Thermodynamics is basically based on the Law of Conservation of Energy.

QUESTION: 2

A PMM1 is

A.
A thermodynamic machine
B.
A hypothetical machine
C.
A real machine
D.
A hypothetical machine whose operation would violate the first law of thermodynamic

Solution:

There can be no machine which would continuously supply mechanical work without some other form of energy disappearing simultaneously. It is fictitious machine.

QUESTION: 3

In a cyclic process, heat transfer are +15.7 kJ, -26.2 kJ, -4.86 kJ and +31.5 kJ. What is the network for this cyclic process?

A.
15.14 kJ
B.
16.41 kJ
C.
16.14 kJ
D.
15.41 kJ

Solution:

QUESTION: 4

A stationary mass of gas is compressed without friction from an initial state of 0.3 m³ and 0.1 MPa to a final state of 0.15 m³ and 0.1 MPa, the pressure remaining constant during the process. There is a transfer of 40 kJ of heat from the gas during the process. What is the change in internal energy of the gas?

A.
-5 kJ
B.
+25 kJ
C.
-25 kJ
D.
+15 kJ

Solution:

= 0.1 χ 10⁶ (0.15-0.3)
= -15Kj
-25Kj

QUESTION: 5

An engine is tested by means of a water brake at 1000 rpm. The measured torque-of the engine is 10000 Nm and the water consumption of the brake is 0.5 m3/s, its inlet temperature being 25°C. Assuming that the whole of the engine power is ultimately transferred into heat which is absorbed by the cooling water, what is the water temperature at exit?

A.
22.5°C
B.
23.5°C
C.
24.5°C
D.
25.5°C

Solution:

Engine power,

QUESTION: 6

What reaction takes place during photosynthesis?

A.
Exothermic reaction
B.
Redox reaction
C.
Endothermic reaction
D.
Combustion reaction

Solution:

Photosynthesis takes place by absorbing heat and energy from the surroundings. Since, endothermic reaction is a reaction in which the system absorbs heat from its surroundings, the reaction that takes place during photosynthesis is an endothermic reaction.

QUESTION: 7

What is the temperature rise after 5 minutes in the below volume?

A.
423°C
B.
378°C
C.
224°C
D.
287°

Solution:

Energy in = Energy out

Energy in = 10 x 100 x 5 x 60 + 10 x 50 x 5 x 60 = 450 kJ

QUESTION: 8

Energy is added to 5 kg of air with a paddle wheel so that ΔT = 100°C while P = const. in an insulated container. The paddle-wheel work is

A.
500 kJ
B.
482 kJ
C.
412 kJ
D.
358 kJ

Solution:

–W = mΔh

= 5 × C_pΔT

= 5 × 1.0 × 100

= 500 kJ

QUESTION: 9

An ideal gas of mass m at state 1 expands to state 2 via three paths. If QA, QB and Qc represent the heat absorbed by the gas along three paths, then

A.
Q_A < Q_B < Q_C
B.
Q_A > Q_B > Q_C
C.
Q_A < Q_B > Q_C
D.
Q_A > Q_B < Q_C

Solution:

QUESTION: 10

The values of heat and work transfer for the flow processes of a thermodynamic cycle are given below:

The thermal efficiency and work ratio for the cycle will be respectively

A.
33% and 0.66
B.
66% and 0.36
C.
36% and 0.66
D.
33% and 0.36

Solution:

Test: First Law of Thermodynamics - 1

10 Questions MCQ Test Thermodynamics | Test: First Law of Thermodynamics - 1

The first law of thermodynamics is the law of

A PMM1 is

In a cyclic process, heat transfer are +15.7 kJ, -26.2 kJ, -4.86 kJ and +31.5 kJ. What is the network for this cyclic process?

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