- #1

Dx

is 1.8Kw right?

e=W/q_h

.30 * 600

TY

dx

You are using an out of date browser. It may not display this or other websites correctly.

You should upgrade or use an alternative browser.

You should upgrade or use an alternative browser.

- Thread starter Dx
- Start date

- #1

Dx

is 1.8Kw right?

e=W/q_h

.30 * 600

TY

dx

- #2

Tom Mattson

Staff Emeritus

Science Advisor

Gold Member

- 5,500

- 8

No, that would correspond to an efficiency of 0.33...

- #3

Dx

Originally posted by Tom

No, that would correspond to an efficiency of 0.33...

Is my equation wrong, what am i doing incorrectly tom?

Dx

- #4

Tom Mattson

Staff Emeritus

Science Advisor

Gold Member

- 5,500

- 8

Originally posted by Dx

Is my equation wrong, what am i doing incorrectly tom?

Dx

I can't tell, since I don't know the meanings of the symobls you used. Efficiency is power output divided by power input.

- #5

Dx

Originally posted by Dx

A heat engine has efficiency of 30% and its power is 600W. what is the rate of heat input?

is 1.8Kw right?

e=W/q_h

.30 * 600

yourt the man Tom! Thats what my symbols mean. e= efficiency, W=work ouot/Q_h=work in. so why did i get this wrong, tom.

Im lost in the math and dont know where? plz help?

Dx

- #6

HallsofIvy

Science Advisor

Homework Helper

- 41,833

- 963

In this case, the formula you give is: e=W/q_h and the values are efficiency= e= 0.30, Work out= W= 600.

In other words, 0.30= 600/q_h. Solving that, 0.30*q_h= 600 so

q_h= 600/0.30= 2000 Joules.

It should occur to you that, since efficiency is always less than 1, there must be more energy put in that you get out.

.30 * 600

- #7

Tom Mattson

Staff Emeritus

Science Advisor

Gold Member

- 5,500

- 8

Originally posted by HallsofIvy

You might be better off to take Tom's answers with a grain of salt and check them carefully. He seems to be doing the same thing you are: taking the numbers given and putting them together in the simplest way without regard for the correct formula.

No, Dx was quoting himself (not me) in his post above. The only "answer" I gave was...

"I can't tell, since I don't know the meanings of the symobls you used. Efficiency is power output divided by power input."

...which is no different from what you posted.

- #8

- 1,036

- 1

Speaking of grains of salt,Originally posted by HallsofIvy

You might be better off to take Tom's answers with a grain of salt and check them carefully.

600 watts/30% = 2,000

- #9

Share: