Electrical Formulas

OHM’S LAW A description of the relationship between voltage, current, and resistance, where:

E stands for voltage (or “electromotive force”)

I stands for current, and

R stands for resistance.

Ohm’s Law is expressed thusly:

E = IR

So, if we know that our voltage is 120V and our current is 20A, we can calculate the resistance:

120 = 20xR

120/20 = 6

Therefore, our resistance is 6 ohms. Since the mathematical symbol for “ohm” is the Greek letter

Omega, we write this answer as:

6!

THE POWER EQUATION Describes the relationship between wattage, current, and voltage, where:

E stands for voltage (or “electromotive force”)

I stands for current, and

P stands for wattage (or “power”)

Because of these symbols, the Power Equation is often referred to as the “PIE” formula:

P=IE

If, as in the above example, our voltage is 120V and our current is 20A, we can use the Power Equation to calculate the wattage:

P = 20 x 120

20 x 120 = 2400

…So our power is 2400W.

If, however, our voltage is 240V and our current is 10A, the equation looks like this:

P = 10 x 240

10 x 240 = 2400

…So our power is still 2400W.

The Power Equation is also known as the “West Virginia” formula, because it can also be  expressed with these symbols:

W=VA