What is the Electricity Formula Wheel? This is sometimes called *Resistance Formula Wheel* or simply *Formula Wheel*. But for the purpose of specificity, we will use the **“Electricity Formula Wheel”**. It is used as reference to solve for the unknown value in an electrical circuit to help builders and maintenance teams design, install, repair and properly implement electrical systems and applications. This formula covers the four major areas involved in a circuit, namely, Voltage, Current, Resistance and Power.

Resistance in relation to Voltage and Current has been discussed in the two previous lessons, extracting the needed formulas and converting them into a **Triangle Formula**. In this lesson and in the next three, we will discuss how to use the same principle in calculating the relationship between **Power**, **Current** and **Voltage**.

As in Ohm’s Law, the same principle applies in calculating the Power, Voltage and Current where the use of the formulas can only give the correct answer when the correct values are used. So always remember the following four rules:

– Current is always expressed in Amperes or amps

– Voltage is always expressed in Volts

– Resistance is always expressed in Ohms

– Power is always expressed in Watts

With these rules, the decimal equivalent of figures that are less than 1 should be converted. For example, if the circuit’s voltage is 10 and the current is 200 mA (200 milliamp), the decimal equivalent of the 200 mA, which is 0.2 Amp, should be used in the calculation.

In the next three lessons, we will extract, or individualize, the formulas for Power, Voltage and Current into their triangle formula versions. Then we will use these to solve for the unknown values.