Ohms Law

We know that current is flowing in a circuit. It would be handy sometimes to be able to figure out how much current is flowing. It turns out there is an equation that links voltage to current and resistance. That equation is called Ohms Law.

Ohms Law will seem difficult to grasp at first. Do not be disappointed if you do not understand it completly. The purpose of this guide is to introduce you to Ohms Law so that you can understand why it is important. As you progress in your knowledge of electronics, you should return to this guide a few times to remind yourself of what Ohms Law means.

The Law

Here is Ohms Law, in its most common form.

Ohms Law: V = I x R

In Ohms Law, V stands for Voltage and R stands for Resistance. Those 2 are easy. The hard one to remember is that I stands for Current. This equation tells us that Voltage equals Current times Resistance. If we know current and resistance, we can calculate voltage.

Using algegra, we can express Ohms Law in 2 other forms. Lets look at those forms now.

Ohms Law, form 2: R = V / I

In this form, Ohms law is telling us that Resistance is equal to Voltage divided by Current. In this form if we know voltage and current we can calculate resistance.

Ohms Law, form 3: I = V / R

Finally, this equation tells us that Current equals Voltage divided by Resistance.

If you are familiar with algebra then you may notice that all 3 forms are really the same equation. If you are not familiar with algebra then you will just have to take my word for it. You can use any of the above 3 equations any time you need to use Ohms Law. They are interchangeable.