COMS-201: Amateur Radio Technician
DAY 1

Understanding Ohm's Law

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What Is Ohm’s Law?

Ohm’s Law is an incredibly useful formula that describes the relationship between voltage, current, and resistance.

Let’s break it down:

  1. Voltage (E): Imagine voltage as the push that makes electrons move. It’s like the water pressure in a hose—the higher the pressure, the faster the water flows.

  2. Current (I): Current is the flow of electrons. Think of it as the water streaming through the hose. The more electrons (current), the brighter the light bulb or the louder the speaker.

  3. Resistance (R): Resistance is like the narrowness of the hose. If the hose is wide (low resistance), water flows easily. If it’s narrow (high resistance), water struggles to get through.

Ohm’s Law Equation

As stated earlier, Ohm’s Law is a mathematical formula that shows the exact relationship between these three things.

E = I × R

  • E: Voltage (in volts)

  • I: Current (in amperes or amps)

  • R: Resistance (in ohms)

The formula can be rearranged to describe any of the three terms by the relationship of the other two.

I = E / R

R = E / I

Ohm’s Law Triangle

A great way to remember the relationship described by Ohm’s Law is to draw a simple triangle chart. Start by drawing a triangle with E, I, and R at the corners like so.

Now cover the unit you are solving for with your finger, and the other two will guide you.

  • If you need to find voltage (E), cover E, and you get: E = I × R.

  • If you need to find current (I), cover I, and you get: I = E / R.

  • If you seek resistance ®, cover R, and you get: R = E / I.

It might be useful to draw this triangle on your exam answer sheet right when you start your test so that it is available for reference during the exam.