Ohm's law calculations

Summary
Ohms Law states that: I = V/R where I is the current in amperes, V is the potential difference in volts, and R is a resistance, measured in ohms. Ohm's Law gives an accurate method of determining values in an electrical circuit.

Solving Ohm's law

Using the rules of Ohm's Law gives an accurate method of determining values in an electrical circuit. To assist with these problems use this solving triangle.

Ohm's law calculations solving triangle

If the value of E and I are known, then to find R, E is divided by I. Similarly, if E and R are known, then I is found by dividing E by R. If I and R are known, then E is found by multiplying I by R.

Circuit diagram resistance value unknown

In the circuit diagram above the value of the resistance is not known. The Applied voltage is 12 V and the current flow is 4 A. To find the value of R simply divide E by I, or 12 by 4. The value of R is 3 ohms (Ω).

Circuit diagram applied voltage value unknown

In the circuit diagram above the value of the applied voltage is not known but the amperage and resistance are. To find the value of E, multiply I by R, or 6 A X 4 Ω. The answer is 24 V.

Circuit diagram current flow value unknown

In the circuit diagram above the value of the current flow is unknown. To find the value of I, divide E by R, or in this case, 12 V divided by 3 Ω. The value of I is 4 A.