Ohm's Law:


This is a very basic explanation of Ohm's Law. For a complete, confusing definition you can go here. This explanation is for the newb.


Basic Ohms law has three parts:

1. The formula:


E=I*R (EIR) [pronounced like ear)

I remember it as "Pie in the ear".


2. The hard part is remembering what the letters mean.

P= Power

I= Current

E= Potential Difference

R= Resistance

3. units of measurement.

Just like weight is measured in pounds, and volume is measured in liters the units above have a way to measure them:

Power- Watts

Current- Amps

Potential- Volts

Resistance- Ohms

That is the basic part of ohm's law. If you learn the information above you will be able to pass any question you come across. If you don't want to remember all of that and all you want to do is pass the test then remember the following:


Watts=Amps * Volts

Volts= Amps * Ohms


One can remember it like this: "Women Always Vote; Voting's Always Open".

This way when you get a question on the test that asks:

If the rated power of a power supply is 140 watts and the supply is running at 14 volts; how much current can be drawn from the supply?

a. 5 amps

b. 10 amps

c 12 amps

d 15 amps


Use the formula above to figure it out. You have the watts and the volts; all of the answers are in amps. You need the formula that has these values: Watts=Amps * Volts

Substituting the values in one gets:

140=14 * A

Using simple algebra we simplify this to A=140/14 or Amps= 10

Note: If you need help with Algebra this is well out of the scope of this article. Obtain help from someone who knows.


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