A 40-gallon electric water heater has a 10kW heating element. What will the water temperature be after 15 min of heating if the start temp is 50F degrees.
There must be an equation. I can't find it in notes or text.
Tell me more
×
Physics Stack Exchange is a question and answer site for
active researchers, academics and students of physics. It's 100% free, no registration required.
|
|
|||||||||||
|
closed as too localized by David Zaslavsky♦ Jan 23 '12 at 20:29
This question is unlikely to help any future visitors; it is only relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation that is not generally applicable to the worldwide audience of the internet. For help making this question more broadly applicable, see the FAQ.
|
You need to know these things to solve the problem:
\begin{equation} P = \frac{dW}{dt} \end{equation} where W is energy (here: the amount of electric energy transformed into heat by the heater), P power (here: of the heater) and t time.
\begin{equation} c_w = \frac{1}{m} \frac{Q}{\Delta T} \end{equation} where cw is specific heat capacity of substance w (here: water), m is the mass of the the heated substance, Q heat transferred and T temperature. In your assignment heater has constant power so the first derivative can be replaced by difference quotient. You can use the first equation to calculate the amount of heat transferred from the heater to water and the second equation to calculate the effect the heat has on water in terms of temperature change. |
|||
|
|
