Rate of energy radiated per second

[rasen58]

If the temperature of a star increases from 10,000K to 30,000K, by what factor will the rate of energy radiated per second increase?

What formula am I supposed to use to determine this?

[studiot]

It's called Stephan's Law.

 

http://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law

 

or since Wiki makes a meal of it

 

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html

[rasen58]

I saw that before, but I don't understand how that works for this problem.

The answer is 8, but if you first use the equation by setting T = 10,000 and then setting T = (30,000-10,000), wouldn't you get a factor increase of 16, and not 8?

Edit: Oh never mind, I read the answer wrong. It's 81, so I guess you'd have to use T=30,000 and 3^4 = 81, which makes sense.

Edited December 20, 2014 by rasen58

[studiot]

Are you sure someone didn't say the factor was 80, not 8?

 

I make it 81 using a simple straightforward ratio.

 

 

setting T = 10,000 and then setting T = (30,000-10,000),

Please note that T means either temperature or temperature difference, but not both.

 

Edit

I see you read the question properly whilst I was working it out and posted more in your post#3.

 

Edited December 20, 2014 by studiot