Question 1

How much work will need to be input to extract 5.0 J of heat from the cold reservoir of a Carnot refrigerator operated between 20S1U1P1$\circ$S1S1P0C and 0S1U1P1$\circ$S1S1P0C?

Accepted Answer

A) 0.23 J 
B) 0.37 J 
C) 0.56 J 
D) 0.68 J 
E) 0.71 J 
A) 0.23 J 
B) 0.37 J 
C) 0.56 J 
D) 0.68 J 
E) 0.71 J

Question 2

How much work will need to be input to expel 5.0 J of heat to the hot reservoir of a Carnot heat pump operated between 20S1U1P1$\circ$S1S1P0C and 0S1U1P1$\circ$S1S1P0C?

Accepted Answer

A) 0.23 J 
B) 0.37 J 
C) 0.56 J 
D) 0.68 J 
E) 0.34 J 
A) 0.23 J 
B) 0.37 J 
C) 0.56 J 
D) 0.68 J 
E) 0.34 J

Question 3

Two six-sided dice are rolled and the two numbers are added together.What is the probability of getting a total of seven?

Accepted Answer

A) 1/36 
B) 1/12 
C) 1/6 
D) 7/12 
A) 1/36 
B) 1/12 
C) 1/6 
D) 7/12

Question 4

If 5.0 J of heat are extracted from the cold reservoir of a Carnot refrigerator operated between 20S1U1P1$\circ$S1S1P0C and 0S1U1P1$\circ$S1S1P0C,how much heat is expelled into the hot reservoir?

Accepted Answer

A) 4.66 J 
B) 2.02 J 
C) 5.37 J 
D) 3.23 J 
E) 0.71 J 
A) 4.66 J 
B) 2.02 J 
C) 5.37 J 
D) 3.23 J 
E) 0.71 J

Question 5

A Carnot engine uses reservoirs at temperatures of 27.0S1U1P1$\circ$S1S1P0C and 327S1U1P1$\circ$S1S1P0C.In one cycle,it uses 600 J of heat from the high temperature reservoir.How much work does it do in one cycle?

Accepted Answer

A) 300 J 
B) 354 J 
C) 550 J 
D) 600 J 
A) 300 J 
B) 354 J 
C) 550 J 
D) 600 J

Question 6

A nuclear submarine uses its reactor to heat water/steam to a temperature of 950S1U1P1$\circ$S1S1P0C.The steam drives turbines that turn the submarines propellers.After the steam passes through the turbines it is cooled to 4S1U1P1$\circ$S1S1P0C and condensed by the seawater that surrounds the submarine and returned to be heated by the reactor again.What is the upper limit of the efficiency of the submarine's turbines?

Accepted Answer

A) 21.7% 
B) 38.6% 
C) 77.4% 
D) 85.1% 
E) 99.6% 
A) 21.7% 
B) 38.6% 
C) 77.4% 
D) 85.1% 
E) 99.6%

Question 7

One end of a metal rod is in contact with a reservoir at a 400K and the other end in contact with a reservoir at 100K.The rod and reservoirs make up a closed system.If 5500 J are conducted from one end to the other uniformly (no change in temperature along the rod)what is the change in entropy of the system?

Accepted Answer

A) 8.56 J/K 
B) 10.9 J/K 
C) 25.4 J/K 
D) 41.3 J/K 
E) 68.8 J/K 
A) 8.56 J/K 
B) 10.9 J/K 
C) 25.4 J/K 
D) 41.3 J/K 
E) 68.8 J/K

Question 8

An engine exhausts 600 J of of heat to the cold temperature reservoir and has an efficiency of 25%.How much heat does it take in from the high temperature reservoir?

Accepted Answer

A) 800 J 
B) 650 J 
C) 400 J 
D) 2400 J 
A) 800 J 
B) 650 J 
C) 400 J 
D) 2400 J

Question 9

Six coins are flipped simultaneously.Calculate the change in entropy of this system in units of kB if another coin is added.

Accepted Answer

A) 0.5 
B) 2.0 
C) 1.0 
D) 0.7 
E) 0.8 
A) 0.5 
B) 2.0 
C) 1.0 
D) 0.7 
E) 0.8

Question 10

An engine exhausts 600 J of of heat to the cold temperature reservoir and has an efficiency of 25%.How much work is done by the engine?

Accepted Answer

A) 200 J 
B) 800 J 
C) 650 J 
D) 400 J 
A) 200 J 
B) 800 J 
C) 650 J 
D) 400 J

Question 11

One end of a metal rod is in contact with a reservoir at a 400 K and the other end in contact with a reservoir at 100 K.The rod and reservoirs make up a closed system.If 5500 J are conducted from one end to the other uniformly (no change in temperature along the rod)what is the change in entropy of the rod?

Accepted Answer

A) 0.0 J/K 
B) 18.3 J/K 
C) 21.1 J/K 
D) 34.4 J/K 
E) 37.2 J/K 
A) 0.0 J/K 
B) 18.3 J/K 
C) 21.1 J/K 
D) 34.4 J/K 
E) 37.2 J/K

Question 12

Electrons have a property called spin that can either be up or down,analogous to how a coin can be heads or tails.Consider 6 electrons.Calculate the entropy for the case where four spins are up and two are down.

Accepted Answer

A) 1.4 * 10-23 J/K 
B) 2.2 * 10-23 J/K 
C) 1.1 * 10-23 J/K 
D) 4.6 * 10-23 J/K 
E) 3.7 * 10-23 J/K 
A) 1.4 * 10-23 J/K 
B) 2.2 * 10-23 J/K 
C) 1.1 * 10-23 J/K 
D) 4.6 * 10-23 J/K 
E) 3.7 * 10-23 J/K

Question 13

A heat pump has a coefficient of performance of 6.If the heat pump absorbs 50 cal of heat from the cold outdoors in each cycle.Evaluate the heat expelled to the warm indoors.

Accepted Answer

A) 40 cal 
B) 48 cal 
C) 50 cal 
D) 58 cal 
E) 60 cal 
A) 40 cal 
B) 48 cal 
C) 50 cal 
D) 58 cal 
E) 60 cal

Question 14

A Carnot engine uses reservoirs at temperatures of 27.0S1U1P1$\circ$S1S1P0C and 327S1U1P1$\circ$S1S1P0C.In one cycle,it uses 1200 J of heat from the high temperature reservoir.How much heat is exhausted to the low temperature reservoir in one cycle?

Accepted Answer

A) 300 J 
B) 354 J 
C) 550 J 
D) 600 J 
A) 300 J 
B) 354 J 
C) 550 J 
D) 600 J

Question 15

A bartender mixes 0.1 liter of alcohol which is at room temperature (= 300 K)with 0.3 liter of soda water out of the refrigerator (temperature = 280 K).In this process,

Accepted Answer

A) the entropy of the water increases and that of the alcohol increases. 
B) the entropy of the water decreases and that of the alcohol increases. 
C) the entropy of the water increases and that of the alcohol decreases. 
D) the entropy of the water decreases and that of the alcohol decreases. 
E) Not enough information given,because the specific heat capacities of water and alcohol will decided which entropy will increase,and which will decrease. 
A) the entropy of the water increases and that of the alcohol increases. 
B) the entropy of the water decreases and that of the alcohol increases. 
C) the entropy of the water increases and that of the alcohol decreases. 
D) the entropy of the water decreases and that of the alcohol decreases. 
E) Not enough information given,because the specific heat capacities of water and alcohol will decided which entropy will increase,and which will decrease.

Question 16

A refrigerator has a coefficient of performance of 6.If the refrigerator absorbs 50 cal of heat from the cold reservoir in each cycle,evaluate the heat expelled into the heat reservoir.

Accepted Answer

A) 40 cal 
B) 48 cal 
C) 50 cal 
D) 58 cal 
E) 60 cal 
A) 40 cal 
B) 48 cal 
C) 50 cal 
D) 58 cal 
E) 60 cal

Question 17

An 800-kg car traveling at 25 m/s crashes into a wall on a hot day (27S1U1P1$\circ$S1S1P0C).What is the total change in entropy?

Accepted Answer

A) 39 J/K 
B) 67 J/K 
C) 830 J/K 
D) 1700 J/K 
E) 9300 J/K 
A) 39 J/K 
B) 67 J/K 
C) 830 J/K 
D) 1700 J/K 
E) 9300 J/K

Question 18

An ideal Carnot engine takes in 160 kcal of heat at 100S1U1P1$\circ$S1S1P0C and exhausts some of this at 35S1U1P1$\circ$S1S1P0C.How much work must have been done by the engine?

Accepted Answer

A) 76.0 kJ 
B) 116.7 kJ 
C) 236.6 kJ 
D) 287.6 kJ 
E) 307.6 kJ 
A) 76.0 kJ 
B) 116.7 kJ 
C) 236.6 kJ 
D) 287.6 kJ 
E) 307.6 kJ

Question 19

An engine takes in 600 J of heat from the high temperature reservoir and exhausts 400 J to the low temperature reservoir.What is the work done by this engine?

Accepted Answer

A) 1000 J 
B) 200 J 
C) 400 J 
D) 700 J 
A) 1000 J 
B) 200 J 
C) 400 J 
D) 700 J

Question 20

A 0.750-kg iron bar is taken from a forge at 900S1U1P1$\circ$S1S1P0C and dropped into 14.00 kg of water at 20.0S1U1P1$\circ$S1S1P0C.Assuming that no energy is lost by heat to the surroundings as the water/iron reaches their final temperature,determine the total entropy change of the iron bar plus-water system.Assume that specific heat of iron is 448 J/(kg.K).

Accepted Answer

A) 371 J/K 
B) 444 J/K 
C) 534 J/K 
D) 622 J/K 
E) 756 J/K 
A) 371 J/K 
B) 444 J/K 
C) 534 J/K 
D) 622 J/K 
E) 756 J/K

Exam 20: The Second Law of Thermodynamics

How much work will need to be input to extract 5.0 J of heat from the cold reservoir of a Carnot refrigerator operated between 20 ∘\circ∘ C and 0 ∘\circ∘ C?

How much work will need to be input to expel 5.0 J of heat to the hot reservoir of a Carnot heat pump operated between 20 ∘\circ∘ C and 0 ∘\circ∘ C?

Two six-sided dice are rolled and the two numbers are added together.What is the probability of getting a total of seven?

If 5.0 J of heat are extracted from the cold reservoir of a Carnot refrigerator operated between 20 ∘\circ∘ C and 0 ∘\circ∘ C,how much heat is expelled into the hot reservoir?

A Carnot engine uses reservoirs at temperatures of 27.0 ∘\circ∘ C and 327 ∘\circ∘ C.In one cycle,it uses 600 J of heat from the high temperature reservoir.How much work does it do in one cycle?

An engine exhausts 600 J of of heat to the cold temperature reservoir and has an efficiency of 25%.How much heat does it take in from the high temperature reservoir?

Six coins are flipped simultaneously.Calculate the change in entropy of this system in units of kB if another coin is added.

An engine exhausts 600 J of of heat to the cold temperature reservoir and has an efficiency of 25%.How much work is done by the engine?

Electrons have a property called spin that can either be up or down,analogous to how a coin can be heads or tails.Consider 6 electrons.Calculate the entropy for the case where four spins are up and two are down.

A heat pump has a coefficient of performance of 6.If the heat pump absorbs 50 cal of heat from the cold outdoors in each cycle.Evaluate the heat expelled to the warm indoors.

A Carnot engine uses reservoirs at temperatures of 27.0 ∘\circ∘ C and 327 ∘\circ∘ C.In one cycle,it uses 1200 J of heat from the high temperature reservoir.How much heat is exhausted to the low temperature reservoir in one cycle?

A bartender mixes 0.1 liter of alcohol which is at room temperature (= 300 K)with 0.3 liter of soda water out of the refrigerator (temperature = 280 K).In this process,

A refrigerator has a coefficient of performance of 6.If the refrigerator absorbs 50 cal of heat from the cold reservoir in each cycle,evaluate the heat expelled into the heat reservoir.

An 800-kg car traveling at 25 m/s crashes into a wall on a hot day (27 ∘\circ∘ C).What is the total change in entropy?

An ideal Carnot engine takes in 160 kcal of heat at 100 ∘\circ∘ C and exhausts some of this at 35 ∘\circ∘ C.How much work must have been done by the engine?

An engine takes in 600 J of heat from the high temperature reservoir and exhausts 400 J to the low temperature reservoir.What is the work done by this engine?

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Filters

How much work will need to be input to extract 5.0 J of heat from the cold reservoir of a Carnot refrigerator operated between 20^$\circ$C and 0^$\circ$C?

How much work will need to be input to expel 5.0 J of heat to the hot reservoir of a Carnot heat pump operated between 20^$\circ$C and 0^$\circ$C?

If 5.0 J of heat are extracted from the cold reservoir of a Carnot refrigerator operated between 20^$\circ$C and 0^$\circ$C,how much heat is expelled into the hot reservoir?

A Carnot engine uses reservoirs at temperatures of 27.0^$\circ$C and 327^$\circ$C.In one cycle,it uses 600 J of heat from the high temperature reservoir.How much work does it do in one cycle?

Six coins are flipped simultaneously.Calculate the change in entropy of this system in units of k_B if another coin is added.

A Carnot engine uses reservoirs at temperatures of 27.0^$\circ$C and 327^$\circ$C.In one cycle,it uses 1200 J of heat from the high temperature reservoir.How much heat is exhausted to the low temperature reservoir in one cycle?

An 800-kg car traveling at 25 m/s crashes into a wall on a hot day (27^$\circ$C).What is the total change in entropy?

An ideal Carnot engine takes in 160 kcal of heat at 100^$\circ$C and exhausts some of this at 35^$\circ$C.How much work must have been done by the engine?