How much work can be extracted from 5.00 × 10^4 J of heat when 2.00 × 10^4 J of heat is exhausted?

A. - 7.00 × 10^4 J

B. - 3.00 × 10^4 J

C. 3.00 × 10^4 J

D. 7.00 × 10^4 J

***thank you:)

Question

How much work can be extracted from 5.00 × 10^4 J of heat when 2.00 × 10^4 J of heat is exhausted?

A.     -  7.00 × 10^4 J

B.     -  3.00 × 10^4 J

C.       3.00 × 10^4 J

D.       7.00 × 10^4 J

***thank you:)

michele_laino · Answer

I think that we have to apply the first principle of thermodynamics

anonymous · Answer

ok!

michele_laino · Answer

so, we can write this:
$$Q = L + \Delta U$$

michele_laino · Answer

where Q= 2*10^4 Joules, and \Delat U = 5*10^4 Joules

michele_laino · Answer

oops..\Delta*

anonymous · Answer

okay!! so we get 70000? so our solution is choice D?

michele_laino · Answer

no,we have:
$$2 \times {10^4} = L + 5 \times {10^4}$$

anonymous · Answer

ohh oops!!

so we get 20000 = L + 50000
L = - 30000 ? so we solution is choice B?

michele_laino · Answer

yes! That's right!

anonymous · Answer

yay:) thank you!! :)

michele_laino · Answer

thank you!! :D