Thermodynamics Online Objective Test | Thermodynamics Online Objective Test

# Thermodynamics # CBSE 11TH PHYSICS Prepare / Learn

Q1.

A 1.0-kg bar of copper is heated at atmospheric pressure. If its temperature increases from 20 $^{\circ}$ C to 50 $^{\circ}$ C, what is the work done by the copper on the surrounding atmosphere? Given that for Cu $3 α$ = 5.1 x 10-5 / C, $ρ_{C u} = 8.92 \times 10^{3} K g / m^{3}$

ρ_{C u} = 8.92 \times 10^{3} K g / m^{3}

A. 1.6

\times

1 0^{- 2}

B. 1.9

\times

1 0^{- 2}

C. 1.8

\times

1 0^{- 2}

D. 1.7

\times

1 0^{- 2}

Answer : Option D
Explaination / Solution:

ΔV=3αViΔT=5.1×10−5×30×Vi=1.5×10−3ViΔV=1.5×10−3mρCu=1.5×10−318.92×103=1.7×10−7W=PΔV=1.01×105×1.7×10−7=1.7×10−2J

# Thermodynamics # CBSE 11TH PHYSICS Prepare / Learn

Q2.

A 3.00-g copper penny at 25.0 $^{\circ}$ C drops from a height of 50.0 m to the ground. (a) If 60.0percent of the change in potential energy goes into increasing the internal energy, what is its final temperature? Specific heat of Cu $= 0 .385 J / g^{^{\circ}} C$

= 0 .385 J / g^{^{\circ}} C

A. 25.8

^{\circ}

B. 27.8

^{\circ}

C. 26.8

^{\circ}

D. 28.8

^{\circ}

Answer : Option A
Explaination / Solution:

$m g h = 3 \times 1 0^{- 3} \times 10 \times 50 = 1.5 J$

Heat used in increasing temp

$\begin{aligned} Q = 1.5 \times \frac{60}{100} = 0.9 J \\ Q = m s Δ T \\ 0.9 = 3 \times 0.385 \times (T - 298) \\ T = 298.8 K = {25.8}^{\circ} C \end{aligned}$

# Thermodynamics # CBSE 11TH PHYSICS Prepare / Learn

Q3. A water heater is operated by solar power. If the solar collector has an area of 6.00

m^{2}

and the power delivered by sunlight is 550 W/

m^{2}

, how long does it take to increase the temperature of 1.00

m^{3}

of water from 20.0

^{\circ}

C to 60.0

^{\circ}

A. 51.7 ks

B. 48.7 ks

C. 52.7 ks

D. 50.7 ks

Answer : Option D
Explaination / Solution:

$\begin{aligned} Q = m s Δ T \\ P = \frac{W}{t} = \frac{m s Δ T}{t} \end{aligned}$

$t = \frac{m s Δ T}{P} = \frac{1000 \times 4186 \times 40}{550 \times 6} = 50700 \sec = 50.7 K \sec$

# Thermodynamics # CBSE 11TH PHYSICS Prepare / Learn

Q4. A sample of ideal gas is expanded to twice its original volume of 1.00

m^{3}

in a quasi-static process for which

P = α V^{2}

with

α = 5.00 a t m / m^{6}

. How much work is done by the expanding gas?

A. 1.08 MJ

B. 1.28 MJ

C. 0.98 MJ

D. 1.18 MJ

Answer : Option D
Explaination / Solution:

P=αV2α=5.00×1.01×105Vi=1.00m3Vf=2.00m3W=∫1.002.00P.dV=∫1.002.00αV2.dV=[αV33]2.001.00=1.18MJ

# Thermodynamics # CBSE 11TH PHYSICS Prepare / Learn

Q5.

An ideal gas is enclosed in a cylinder with a movable piston on top. The piston has a mass of 8 000 g and an area of 5.00 $c m^{2}$ and is free to slide up and down, keeping the pressure of the gas constant. How much work is done as the temperature of 0.200 mol of the gas is raised from 20.0 $^{\circ}$ C to 300 $^{\circ}$ C?

A. 486 J

P_{i}

B. 476 J

C. 466 J

D. 456 J

Answer : Option C
Explaination / Solution:

in isobaric process

$W = n R (T_{f} - T_{i})$

$W = 0.2 \times 8.31 (300 - 20) = 466 J$

# Thermodynamics # CBSE 11TH PHYSICS Prepare / Learn

Q6. A gas expands from I to F along three possible paths, as indicated in Figure. Calculate the work in joules done by the gas along the paths IAF, IF, and IBF

A. 810 J, 506 J, 203 J

B. 840 J, 536 J, 233 J

C. 820 J, 516 J, 213 J

D. 830 J, 526 J, 223 J

Answer : Option A
Explaination / Solution:

Work done by gas = area under P-V curve

# Thermodynamics # CBSE 11TH PHYSICS Prepare / Learn

Q7. A thermodynamic system undergoes a process in which its internal energy decreases by 500 J. If, at the same time, 220 J of work is done on the system, what is the energy transferred to or from it by heat?

A. Q = -730 J

B. Q = -720 J

C. Q = -700 J

D. Q = -740 J

Answer : Option B
Explaination / Solution:

ΔQ=ΔU+W=(−500)+(−220)=−720J

# Thermodynamics # CBSE 11TH PHYSICS Prepare / Learn

Q8.

Consider the cyclic process depicted in Figure If Q is negative for the process BC, and if $Δ E_{i n t}$ is negative for the process CA, what are the signs of W and $Δ E_{i n t}$ that are associated with BC?

A. 0, +

B. 0, -

C. 0, -

D. +, -

Answer : Option C
Explaination / Solution:

W = area under P-V curve = 0

$\begin{aligned} Δ Q = Δ E_{int} + W \\ W = 0, Δ Q = - v e \\ Δ E_{int} = - v e \end{aligned}$

# Thermodynamics # CBSE 11TH PHYSICS Prepare / Learn

Q9.

Consider the cyclic process depicted in Figure if $Δ E_{i n t}$ is negative for the process CA, what are the signs of Q and W are associated with CA?

A. -, 0

B. -, -

C. +, 0

D. -, +

Answer : Option B
Explaination / Solution:

$W = P Δ V = - v e (i n C o m p r e s s i o n Δ V = - v e)$

$\begin{aligned} Δ Q = Δ E_{i n t} + W \\ Δ E_{i n t} = - v e \\ W = - v e \\ s o t h a t Δ Q = - v e \end{aligned}$

# Thermodynamics # CBSE 11TH PHYSICS Prepare / Learn

Q10. Consider the cyclic process depicted in Figure If Q is negative for the process BC, and if

Δ E_{i n t}

is negative for the process CA, what are the signs of Q, W, and

Δ E_{i n t}

that are associated with AB?

A. +, 0, -

B. -, +, -

C. +, +, +

D. -, 0, +

Answer : Option C
Explaination / Solution:

W = +ve (Expansion)

$\begin{aligned} U_{c} - U_{a} = - v e \\ U_{b} - U_{c} = - v e \\ h e n c e U_{b} - U_{a} = - v e \\ U_{a} - U_{b} = + v e \end{aligned}$

$\begin{aligned} Δ Q = Δ U + W \\ Δ U = + v e \\ W = + v e \\ H e n c e Δ Q = + v e \end{aligned}$

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