- #1
Icheb
- 42
- 0
The circuit in question is this:
http://www.atnetzwerk.de/temp/wasserkocher2.gif
There are two heating elements with a resistance R_0 = 20 Ohm. I have to find R so that the total power output of the heating elements stays the same no matter if I only use one heating element or both.
I first thought of using [tex]R = \frac{R_0 * R_0}{R_0 + R_0}[/tex], but I think that would mean that the power output would be higher when both heating elements are in use. Am I right?
Then I tried solving [tex]R = \frac{U^2}{P}[/tex] for P and doing [tex]U^2 / R_1 = U ^2 / R_2[/tex] for R_1 being the resistance when only one heating element is in use and R_2 being the resistance when both heating elements are in use. Obviously that just leaves me with [tex]R_1 = R_2[/tex], which doesn't help with this problem.
Another approach I tried was just saying that R has to be equal to R_0, because then the maximum available power P would arrive at the resistor at R_0 when only one heating element is in use and P/2 would arrive at each of them when both of them are turned on. However I don't know how to prove this or even if this is the right idea at all.
Does anyone have an idea as to how I could solve this problem?
http://www.atnetzwerk.de/temp/wasserkocher2.gif
There are two heating elements with a resistance R_0 = 20 Ohm. I have to find R so that the total power output of the heating elements stays the same no matter if I only use one heating element or both.
I first thought of using [tex]R = \frac{R_0 * R_0}{R_0 + R_0}[/tex], but I think that would mean that the power output would be higher when both heating elements are in use. Am I right?
Then I tried solving [tex]R = \frac{U^2}{P}[/tex] for P and doing [tex]U^2 / R_1 = U ^2 / R_2[/tex] for R_1 being the resistance when only one heating element is in use and R_2 being the resistance when both heating elements are in use. Obviously that just leaves me with [tex]R_1 = R_2[/tex], which doesn't help with this problem.
Another approach I tried was just saying that R has to be equal to R_0, because then the maximum available power P would arrive at the resistor at R_0 when only one heating element is in use and P/2 would arrive at each of them when both of them are turned on. However I don't know how to prove this or even if this is the right idea at all.
Does anyone have an idea as to how I could solve this problem?
Last edited by a moderator: