Ohm's Law, named after Georg Ohm, a German mathematician and physicist B.
1789 D. 1854 - Bavaria, defines the fundamental relationship between power,
voltage, current and resistance. These are the very basic electrical units we
work with, and are the very same principles that apply to direct current,
alternating current, and radio frequency alike.
Ohm's Law Wheel
E = Voltage (sometimes "U" or "V" are used instead of "E", and measured in
To make your calculations even easier, use the handy and useful
"Ohm's Law Calculator".
Example of Use
Let's say...you have a small room heater that blows out the circuit breaker whenever it's on for more than an hour. Why? Well...you know that the voltage coming to your home is 220V and the heater has a sticker on it, rating the power at 2500 watts. After checking, the outlet you are plugging the heater into is controlled by a 10A breaker. So now what? Pick out the appropriate formula, from the "Ohm's Law Wheel" above to find the current (or even easier, stick everything into the calculator). The formula we need is: I = P/E so we have I = 2500 /220. I = 11.36A. Now you see that your heater is pulling over 11A. on a 10A breaker, causing the breaker to jump after a while. To figure out the resistance of the heating element, simply pick out one of the fitting formulas from the wheel above to find R. R = E/I R = 220/11.36 R= 19.36 ohms. Due to the fact that we are using AC current, all the above results are not exact.