Thermodynamics
Refrigerator (reversed Carnot)
Run in reverse: work in pumps heat cold→hot (COP = Tc/(Th−Tc)).
Refrigerator (reversed Carnot) — interactive Thermodynamics simulation. Run in reverse: work in pumps heat cold→hot (COP = Tc/(Th−Tc)). Free browser-based virtual physics lab with live SI measurements and a guided tutorial.
Refrigerator COP
Run in reverse: work in pumps heat cold→hot (COP = Tc/(Th−Tc)).
A refrigerator is a heat engine run backward: electrical work drives heat from the cold interior to the warm room. Coefficient of performance COP = Q_c/W can exceed 1 because heat pumped is larger than work supplied—unlike efficiency, which is always ≤ 1.
- COP = T_c/(T_h−T_c)
- Work input
Investigation brief
Plan the question before you open the lab
The brief mirrors the prerendered page: driving question, competing predictions, variable roles, governing laws, setup, analysis and extension prompts remain visible and in this order.
Driving question
Running the Carnot cycle backward turns an engine into a refrigerator — net work goes IN instead of coming out. Does the gas still absorb heat from the cold reservoir, like a real fridge pulling heat out of its interior?
Predictions to weigh
- No — reversing the cycle also reverses which reservoir absorbs heat.
- A reversed cycle doesn't exchange heat with either reservoir.
- Yes — the reversed cycle absorbs heat from the cold side and dumps more heat into the hot side, using the input work to do it.
Variable roles
What you set:
- Leg number
What you measure:
- Leg's target volume V (L)
- Work done by gas this leg (J)
How the investigation runs
- Open the carnot-fridge preset and press Reset. The same 4 legs as carnot-cycle run in reverse order.
- Enable the per-leg work readout, and the cooling/heating COP readouts.
- For each leg of the cycle (1 through 4), read off the leg's target volume and the work done by the gas during that leg.
Governing equation
Refrigerator Coefficient of Performance — COP = Tc / (Th − Tc)
A reversed Carnot cycle's cooling performance is measured by COP_cool = Tc/(Th − Tc): how much heat is removed from the cold space per unit of work supplied. Smaller temperature gaps give better (higher) COP.
What the printable worksheet asks students to work out
- Sum your 4 legs' work values — the total (net work done BY the gas) should come out negative, meaning net work must be supplied TO the gas. Compute the cooling COP = Tc/(Th − Tc) = 300/(600−300) = 1.0 and heating COP = Th/(Th − Tc) = 2.0.
- Compare the leg order here to carnot-cycle's leg order. Explain how simply reversing the sequence of the same 4 legs flips the cycle from an engine (net work out) into a refrigerator (net work in).
Where this shows up beyond the lab
- A cooling COP of 1.0 means the fridge moves 1 J of heat out of the cold space for every 1 J of work supplied. A heating COP of 2.0 (heat pump mode) means it delivers 2 J of heat to the warm space per 1 J of work. Explain why COP_heat is always exactly 1 more than COP_cool for the same reservoirs.
- Unlike engine efficiency (always ≤ 1), COP can exceed 1 — that's not a violation of energy conservation. Explain why COP > 1 is possible: the extra energy delivered comes from the reservoir being cooled, not created from nothing.
- AP Physics 2 — Unit 9: Thermodynamics
- IB Physics — B.4 Thermodynamics
- General High School Physics — Heat, temperature & gas laws
- NGSS High School Physics — Thermal energy transfer
- Welcome to Carnot Fridge
- Select the chamber
- Press Play
- Refrigerator COP
- Open the Properties panel
- You did it!
Open the interactive simulation to build the scene, press Play, and explore with live measurements and a guided tutorial.
Heat Engines & Carnot Efficiency