# Heat Engine Carnot Efficiency question

1. May 17, 2012

### DrDonaldDuck

1. The problem statement, all variables and given/known data
A heat engine has a carnot efficiency of 0.11. How much internal energy does this engine use in order to do 5.1 x 10^4 joules of work? How much heat does this engine give off/exhaust?

2. Relevant equations
(change in)U=Q-W
W=(change in)E

2. May 17, 2012

### rock.freak667

You need to post your attempt.

How does W and Q relate to the efficiency?

3. May 17, 2012

### DrDonaldDuck

W is the work done and Q is the heat generated. U is the total internal energy. No idea how to do this, hence my non-existent attempt.

4. May 17, 2012

### DrDonaldDuck

Still stumped and don't know how to attack problem!

5. May 18, 2012

### DrDonaldDuck

EDIT:
I think I got it.
Internal energy=412636J, exhaust heat is the same. So sleepy, please confirm.

Last edited: May 18, 2012
6. May 18, 2012

### rock.freak667

Look up 'thermal efficiency', that will tell you how Q and W are related to the efficiency n.

When you know that you can get the value of Q and subsquently U.