During one operating cycle

PHYSICS · Single correct · AP · Physics 2: Algebra-based · Thermodynamics · Thermodynamics

Problem

During one operating cycle, an electric heat pump uses

1.5\times10^{3}\,\text{J}

of electrical energy to run a compressor. In that cycle,

4.0\times10^{3}\,\text{J}

of energy is removed from the cold indoor air while

5.5\times10^{3}\,\text{J}

of energy is delivered to the warmer outdoor air. Consider two system choices: System X is the indoor air, and System Y is the outdoor air. Which statement about the sign of

Q

for each system during this cycle is most accurate? (a)

Q_X=+4.0\times10^{3}\,\text{J}

and

Q_Y=-5.5\times10^{3}\,\text{J}

because energy enters X and leaves Y. (b)

Q_X=-5.5\times10^{3}\,\text{J}

and

Q_Y=+4.0\times10^{3}\,\text{J}

because more energy is removed from X than from Y. (c)

Q_X=-4.0\times10^{3}\,\text{J}

and

Q_Y=+5.5\times10^{3}\,\text{J}

because energy leaves X and enters Y. (d)

Q_X=0

and

Q_Y=0

because the process conserves energy.

Related theory

Browse the problem library