A heat engine does work by using a gas at an initial pressure of 1000 Pa and vol

Question

A heat engine does work by using a gas at an initial pressure of 1000 Pa and volume .1m 3. Step-by-step, it then increases the pressure to 10,000 Pa (at constant volume), increases the volume to .15m3 (at constant pressure), decreases the pressure back to 1,000 Pa (at constant volume) and returns the volume back to .1m3 (at constant pressure).

1)  How much work is done by the gas during the first step?

a) W = 0 J

b) W = 450 J

c) W = 500 J

d) W = 750 J

e) W = 1250 J

f) W = 1350 J

2)  How much work is done by the gas during the second step?

a) W = 0 J

b) W = 450 J

c) W = 500 J

d) W = 750 J

e)W = 1250 J

f) W = 1350 J

3)  How much work is done by this heat engine in one complete cycle?

a) W = 0 J

b) W = 450 J

c) W = 500 J

d) W = 750 J

e) W = 1250 J

f) W = 1350 J

4)  What is the change in internal energy over one complete cycle?

a) DU = 0 J

b) DU = 450 J

c) DU = 500 J

d) DU = 750 J

e) DU = 1250 J

f) DU = 1350 J

5)  How much heat is added to the gas in one complete cycle?

a) Q = 0 J

b) Q = 450 J

c) Q = 500 J

d) Q = 750 J

e) Q = 1250 J

f) Q = 1350 J

A heat engine does 158,000 J of work and gives out 189,000 J of heat to the cold temperature reservoir. The hot and cold temperatures the engine operates at are 382°C and -20° C.

6)  What is the ideal (Carnot) efficiency?

a) 0%

b) 28%

c) 46%

d) 61%

e) 75%

f)100%

7)  What is the actual efficiency?

a) 0%

b) 28%

c) 46%

d) 61%

e) 75%

f)100%

Explanation / Answer

1) W = 0 J because volume is constant)

2)dW=P(dV) = 10000(0.15-0.1) = 500

3)third step dW=P(dV) = 1000(0.15-0.1) = 50 so I just did work=500-50=450J

post other questions separately.

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