So let’s quickly recap the representations for voltage, resistance, and amperage in the Ohm’s Law triangle:

E = Voltage (electromagnetic force)

I = Current (amps)

R = Resistance

For a given resistance, the current is directly proportional to voltage. That said, if you increase the voltage in a circuit with a fixed resistance, the current will increase. If you decrease the voltage in a circuit with a fixed resistance, the current will decrease.

Ohm’s law follows a simple formula:

E = I x R

To quickly recap again; E is voltage, I is current (amps), and R resistance (ohms).

Using Ohm’s Law allows you to find an unknown voltage, current, or resistance as long as you have at least two values of the triangle.

Now, I said you could solve for voltage, current or resistance as long as you have at least two values, yet the formula above only allows for voltage (E) to be solved. Ohm’s Law triangle can be rearranged for different values to be solved.

Solving for unknown voltage: E = I x R

Solving for unknown current: I = E / R

Solving for unknown resistance: R = E / I

When using the triangle, just cover the unknown value with your finger and solve it. Imagine a division symbol under E and a multiplication symbol between I and R.

Example 1: You’re working on a circuit with an unknown voltage. We know the current is 0.5A and the resistance is 10Ω. What’s the voltage?

Keep in mind; we only cover the unknown value we want to solve for. So, we would cover the E in the triangle since we’re trying to determine the voltage. We know we will be using multiplication since we read earlier to imagine a multiplication symbol between I and R.

E = I x R

E = 0.5A x 10Ω

E = 5V

Example 2: You’re working on a circuit with an unknown current. We know the voltage is 5V and the resistance is 10Ω. What’s the current?

Just like earlier, we’re going to cover the symbol we’d like to solve for. So, we will cover the I in the triangle now. We know we will be using division since we read earlier to imagine a division symbol below E

I = E / R

I = 5V / 10Ω

I = 0.5A

Example 3: You’re working on a circuit with unknown resistance. We know the voltage is 5V and the current is 0.5A. What’s the resistance?

Nothing has changed in how we are going to solve this. Just like before, we are going to cover the symbol we’re want to find. So, we would cover the R in the triangle since we need to solve for resistance. We know we will be using division since we read earlier to imagine a division symbol below E

R = E / I

R = 5V / 0.5A

R = 10Ω