Understanding Heat Pumps and Refrigerators

This video tutorial covers basic problems related to heat pumps and refrigerators. It explains how to calculate the coefficient of performance for a refrigerator, determine the maximum coefficient for an ideal refrigerator, and calculate the energy delivered to the hot reservoir. The video also addresses energy transfer in a Carnot refrigerator, including the work needed and the coefficient of performance. Finally, it discusses energy transfer in a heat pump, providing a comprehensive understanding of these thermodynamic systems.

What is the coefficient of performance for a refrigerator that uses 1500 joules of work to absorb 4500 joules from the cold reservoir?

• 2

• 1

• 3

• 4

How do you calculate the maximum coefficient of performance for an ideal Carnot refrigerator?

• Tc/Th

• Th-Tc

• Tc/(Th-Tc)

• Th/Tc

If a refrigerator absorbs 4500 joules from the cold reservoir and uses 1500 joules of work, how much energy is delivered to the hot reservoir?

• 6000 joules

• 4500 joules

• 3000 joules

• 7500 joules

What must be true for the total energy going into and out of an engine to maintain a constant state?

• Energy in and out are irrelevant

• Energy in must be greater

• Energy out must be greater

• Energy in must equal energy out

In a Carnot refrigerator, if 4000 joules are taken from the cold reservoir, how much energy is transferred to the hot reservoir?

• 6000 joules

• 4000 joules

• 5000 joules

• 4444 joules

How much work is needed if a Carnot refrigerator transfers 4444 joules to the hot reservoir and takes 4000 joules from the cold reservoir?

• 400 joules

• 600 joules

• 500 joules

• 444 joules

What is the coefficient of performance for an ideal refrigerator with Tc = 270 K and Th = 300 K?

• 10

• 9

• 7

• 8

A heat pump with a coefficient of performance of 4 uses 2500 joules of work. How much heat energy is transferred to the hot reservoir?

• 10000 joules

• 7500 joules

• 12500 joules

• 5000 joules

How much heat energy is transferred from the cold reservoir to the engine if the heat pump transfers 10000 joules to the hot reservoir and uses 2500 joules of work?

• 5000 joules

• 10000 joules

• 12500 joules

• 7500 joules

What is the relationship between Qh, W, and Qc in a heat pump?

• Qh = Qc - W

• Qh = Qc/W

• Qh = W - Qc

• Qh = W + Qc