Homework Help: physics

Posted by maria on Sunday, January 1, 2012 at 9:39am.

With each cycle, a 2650-W engine extracts 2330 J from a thermal reservoir at 85.1°C and expels 1840 J into a thermal reservoir at 20.9°C.

a) What is the work done for each cycle?

b) What is the engine's efficiency?

c) How much time does each cycle take?

physics - bobpursley, Sunday, January 1, 2012 at 10:26am
a. What does 2650watts mean?
b. eff=(tempIN-TempOUT)/TemOUT in Kelvins
c. work=energy/time

2650=2330/time * efficience
solve for time of cycle
physics - drwls, Sunday, January 1, 2012 at 11:06am
b. Bob Pursley's equation only applies for Carnot cycle engines. Real engines are not built that way. Stirling cycle engine are supposed to come close.

In your case, you should use the actual work out and heat out data.

Wout (per cycle) = Qin - Qout = 490 J
Efficiency = Wout/Qin = 490/2330 = 21.0%

The Carnot cycle formula predicts a maximum possible efficiency of 64.2/358.3 = 17.9%

I note that your heat reservoir temperature is quite low.

Since the stated efficiecy exceeds the Carnot efficiency, the numbers you have been given are not possible.

Answer this Question

Related Questions

physics - An engine absorbs 2000J of heat from a hot reservoir and expels 750J ...
phy - An engine absorbs 2000J of heat from a hot reservoir and expels 750J to a...
Physics - In each cycle of its operation, a heat engine expels 6,100 J of energy...
PHYSICS DUE SOON - In each cycle of its operation, a heat engine expels 6,100 J ...
physics - A Carnot engine is operated between two heat reservoirs at ...
physics - A Carnot engine is operated between two heat reservoirs at ...
Physics - In one cycle a heat engine absorbs 450 J from a high-temperature ...
Physics - In one cycle a heat engine absorbs 530 J from a high-temperature ...
physics - The hot reservoir for a Carnot engine has a temperature of 926 K, ...
Physics - In one cycle, an engine burning a mixture of air and methanol (methyl ...

For Further Reading

First Name:
School Subject:
Answer: