First Law of Thermodynamics MCQ Practice 1

first law of thermodynamics.1st law of thermodynamics.first law of thermodynamics mcq

26. "When a closed system undergoes a thermodynamic cycle, the net heat transfer is equal to net work transfer." This statement is associated with

(a) Pascal's law (b) Zeroth law of thermodynamics (c) Second law of thermodynamics (d) First law of thermodynamics Ans : (d)

27. If a closed system obeys the following from of the First Law equation dq = du+pdv, then : (a) it is undergoing an isentropic process (b) it is pure substance undergoing infinitesimal process (c) it is undergoing an irreversible process (d) it is simple compressible system undergoing

Ans. (d)

28. A sample of ideal gas has an internal energy U and is then compressed to one-half of its original volume while the temperature stays the same. What is the new internal energy of the ideal gas in terms of U? (a) 1/4 U (b) U (c) 1/2 U (d) 4U

Ans. (b)

29. What is the resultant of sum of product of
pressure and volume (PV) with internal energy
U known as?
(a) Enthalpy
(b) Entopy
(c) Specific heat
(d) Work-done

Ans : (a)
H = U + P.V.
dh = du + P.dv
dh = m cpdt
31. General energy equation for system boiler is
given by
(a) Q = H1 + H1
(b) Q = H2 – H1
(c) Q = H2 – H1 + Work done
(d) Q = H2 – H1 + KE

Ans : (b)

32. Which equation correctly represents the steady
flow process where enthalpy, work and heat
are in kJ/kg, velocity is in m/s and gravitational
acceleration is in m/s2?

 

Ans : (c)

33. Which of the following statements hold TRUE
for the first law of thermodynamics?

(a) The entropy of the system remains constant (b) The total energy of the system remains constant (c) The total internal energy of the system remains constant (d) Work done by the system is equal to the heat

Ans : (b) Energy can neither be destroyed nor created, when it disappears in one form it must re–appear at the same time in other forms

34. Enthalpy is an.............. of a system and its unit is............ (a) extensive property, kJ (b) extensive property, kJ/kg (c) intensive property, kJ/ kJ (d) intensive property Ans : (a 35. The heat interaction of the system is a function of temperature only Q = 30 + 1t kJ. If the system does a work of 2 kJ/K. What is the increase in Internal energy per degree temperature? (a) –1 (b) 0 (c) 1 (d) Carnot be determined Ans : (a)