Work Done on Compressing a Gas NEET Questions

Physics - Kinetic Theory of Gases

Work Done on Compressing a Gas MCQ Questions


1.
When a gas is compressed by pushing a piston, the work done BY the gas is:
A.
Positive — gas always does positive work
B.
Zero — no work is done during compression
C.
Negative — volume decreases (ΔV < 0), so ΔW = PΔV < 0
D.
Equal to the heat released
😑 View Answer Rough Work Error
ANSWER :
C. Negative — volume decreases (ΔV < 0), so ΔW = PΔV < 0
2.
The expression for work done BY a gas against constant external pressure P when volume changes from V₁ to V₂ is:
A.
W = PΔV = P(V₂ − V₁)
B.
W = P/(V₂ − V₁)
C.
W = P(V₁ − V₂)
D.
W = P²(V₂ − V₁)
😑 View Answer Rough Work Error
ANSWER :
A. W = PΔV = P(V₂ − V₁)
3.
When work is done ON a gas (compression, ΔW < 0), the First Law of Thermodynamics ΔQ = ΔU + ΔW gives:
A.
ΔU = ΔQ − ΔW = ΔQ + |ΔW| — internal energy increases by both heat input AND work done on gas
B.
ΔU = 0 always during compression
C.
ΔU = −ΔQ
D.
ΔU = ΔQ always
😑 View Answer Rough Work Error
ANSWER :
A. ΔU = ΔQ − ΔW = ΔQ + |ΔW| — internal energy increases by both heat input AND work done on gas
4.
In adiabatic compression (ΔQ = 0), work done ON the gas results in:
A.
Increase in internal energy ΔU = −ΔW > 0, causing temperature rise
B.
Decrease in internal energy
C.
No change in internal energy (ΔU = 0)
D.
Heat release to surroundings
😑 View Answer Rough Work Error
ANSWER :
A. Increase in internal energy ΔU = −ΔW > 0, causing temperature rise
5.
The work done ON a gas (by surroundings) when gas is compressed from V₁ to V₂ at constant pressure P is:
A.
W_on = P²(V₁ − V₂)
B.
W_on = P(V₂ − V₁) (negative for compression)
C.
W_on = P(V₁ − V₂) (positive for compression since V₁ > V₂)
D.
W_on = 0
😑 View Answer Rough Work Error
ANSWER :
C. W_on = P(V₁ − V₂) (positive for compression since V₁ > V₂)
6.
NCERT Exercise 11.6: Two cylinders A (gas at STP) and B (evacuated) are connected via a stopcock. System is thermally insulated. Stopcock opened. Work done BY gas in this free expansion is:
A.
W = (3/2)nRΔT
B.
W = nRT ln(2) (isothermal expansion)
C.
W = 0 — free expansion into vacuum, no opposing force, no work done by or on the gas
D.
W = PΔV (positive, gas expands)
😑 View Answer Rough Work Error
ANSWER :
C. W = 0 — free expansion into vacuum, no opposing force, no work done by or on the gas