# Confusion in understanding how electric heating works

1. Aug 9, 2014

### alditi

I'm working on a project in which I have to build a tiny 4 cm long heater. I did this with copper-windings stuffed in a tiny steel rod. Now I know the power input into this heater is 0.368W, at constant voltage 1.5 volts and the resistance of the heating element is 6.1ohms for a time of 180seconds.

I want to know how to calculate the heat pulse (q) generated in this time. What's the formula for doing this? The internet is unclear. Take this at any distance r from the axis.

2. Aug 9, 2014

### mishima

If there is nothing else in the circuit then the same power input is output. Power is joules of energy per second. So, if you are giving it .368 joules per second over 180 seconds, how many joules is that altogether? Its like if you can run 5 miles per hour and you run 3 hours how many miles have you run?

3. Aug 9, 2014

### sophiecentaur

Did you really use Copper Wire? It is more normal to use resistance wire because copper is such a good conductor that it does not get hot until you put a massive amount of current through it.

Total heat delivered (Energy, in Joules) will be Heater Power in Watts times time in seconds. If you are told the Power, then, as long as you are using the right supply voltage, you don't need to do any more electrical calculations. To check that the Power you are given agrees with the Volts and Resistance, you can use
Power = Volts Squared / Resistance

PS what has "distance r from the axis" got to do with this? IS this something to do with the measurements on the water temperature?