Physics Chapter 15: Misconceptual Questions

About what percentage of the heat produced by burning gasoline is turned into useful work by a typical automobile? (a) 20%. (b) 50%. (c) 80%. (d) 90%. (e) Nearly 100%.

(a) 20%

An ideal gas undergoes an isothermal expansion from state A to page 413), (a)Q = 0, delta U =0, W>0 (b)Q>0, delta U=0, W<0 (c)Q = 0, delta U>0, W>0 (d)Q >0, delta U =0, W>0 (e) Q = 0, delta U<0, W<0

(d)Q >0, delta U =0, W>0

Which of the following possibilities could increase the efficiency of a heat engine or an internal combustion engine? (a) Increase the temperature of the hot part of the system and reduce the temperature of the exhaust. b) Increase the temperatures of both the hot part and the exhaust part of the system by the same amount. (c) Decrease the temperatures of both the hot part and the exhaust part of the system by the same amount. (d) Decrease the temperature of the hot part and increase the temperature of the exhaust part by the same amount. (e) None of the above; only redesigning the engine or using better gas could improve the engine's efficiency.

(a) Increase the temperature of the hot part of the system and reduce the temperature of the exhaust. (c) Decrease the temperatures of both the hot part and the exhaust part of the system by the same amount.

Which statement is true regarding the entropy change of an ice cube that melts? (a) Since melting occurs at the melting point temperature, there is no temperature change so there is no entropy change. (b) Entropy increases. (c) Entropy decreases.

(b) Entropy increases.

An ideal gas undergoes an adiabatic expansion, a process in which no heat flows into or out of the gas. As a result, (a) the temperature of the gas remains constant and the pressure decreases. (b) both the temperature and pressure of the gas decrease. (c) the temperature of the gas decreases and the pressure increases. (d) both the temperature and volume of the gas increase. (e) both the temperature and pressure of the gas increase.

(b) both the temperature and pressure of the gas decrease.

Which is possible:converting (i)100J of work entirely into 100 J of heat, (ii) 100 J of heat entirely into 100 J of work? (a) Only (i) is possible. (b) Only (ii) is possible. (c) Both (i) and (ii) are possible. (d) Neither (i) nor (ii) is possible.

(c) Both (i) and (ii) are possible.

An ideal gas undergoes an isobaric compression and then an isovolumetric process that brings it back to its initial temperature. Had the gas undergone one isothermal process instead, (a) the work done on the gas would be the same. (b) the work done on the gas would be less. (c) the work done on the gas would be greater. (d) Need to know the temperature of the isothermal process.

(c) the work done on the gas would be greater.

An ideal gas under goes an isothermal process. Which of the following statements are true? (i) No heat is added to or removed from the gas. (ii) The internal energy of the gas does not change. (iii) The average kinetic energy of the molecules does not change. (a) (i) only. (b) (i) and (ii) only. (c) (i) and (iii) only. (d) (ii) and (iii) only. (e) (i), (ii), and (iii). (f) None of the above.

(d) (ii) and (iii) only.

On a very hot day, could you cool your kitchen by leaving the refrigerator door open? (a) Yes, but it would be very expensive. (b) Yes, but only if the humidity is below 50% . (c) No, the refrigerator would exhaust the same amount of heat into the room as it takes out of the room. (d) No, the heat exhausted by the refrigerator into the room is more than the heat the refrigerator takes out of the room.

(d) No, the heat exhausted by the refrigerator into the room is more than the heat the refrigerator takes out of the room.

In an isobaric compression of an ideal gas, (a) no heat flows into the gas. b) the internal energy of the gas remains constant. (c) no work is done on the gas. (d) work is done on the gas. (e) work is done by the gas.

(d) work is done on the gas.

A heat engine operates between a high temperature of about 600°C and a low temperature of about 300°C. What is the maximum theoretical efficiency for this engine? (a) = 100%. (b) ~ 66%. (c) ~ 50%. (d) ~ 34%. (e) Cannot be determined from the given information.

(d) ~ 34%.