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Ohm's law is one of the most essential laws of electrical engineering, explaining the relationship between a circuit's resistance, voltage, and current.

## Formula

Basic Ohm's law is calculating the relation between voltage, current, and resistance. The following Ohm's law triangle chart will help to visually remember the equation for calculating each parameter. ^{[1]}

Where:

**V**- is the voltage with an SI unit of**volt,**represented by the letter**V**.**I**- is a current value that flows through a circuit with an SI unit of**ampere**or**amp**and is represented by the letter**A**.**R**- is the resistance with an SI unit of**ohms,**represented by the letter**Ω**.

### Calculate voltage

Here is the equation to find the voltage of a circuit with known current and total resistance: **Voltage (V) = Resistance (R) × Current (I)**.

### Calculate resistance

Here is the equation to find the equivalent resistance of a circuit with known voltage and current: **Resistance (R) = Voltage (V) / Current (I).**

### Calculate current

Here is the equation to find the current flows through a circuit with known voltage and equivalent resistance: **Current (I) = Voltage (V) / Resistance (R).**

## Examples

Calculate the current flows through a light bulb.

What current flows through a 5V flashlight bulb with a resistance of 3.6Ω?

Using the following formula, enter the given values to find the current flowing through the flashlight bulb by knowing its voltage and resistance.

$ \text{Current} = \frac{\text{Voltage}}{\text{Resistance}} $

$ {I} = \frac{V}{R} $

$ {I} = \frac{5V}{3.6Ω} $

$ {I} = 1.39A $

So, the current that flows through the 5V flashlight bulb with 3.6Ω resistance is **I = 1.39A**.

Alternatively, you can use our calculator by going to the **CURRENT** tab, entering the number **5** into the **Voltage (V)** box, **3.6Ω** into the **Resistance (R)**, and instantly getting the current in A, in this case, **1.39A**.

Calculate voltage drops.

Find the voltage drop in an extension cord with a resistance of 0.08Ω with a current flow of 10A.

To find the amount of voltage drop through the extension cord with known current and resistance, use the following formula and enter the given values.

$ \text{Voltage} = \text{Resistance} \times {\text{Current}} $

$ V = R \times I $

$ V = 0.08Ω \times 10A $

$ V = 0.8V $

So, the amount of voltage drops from an extension cord is **V = 0.8V**.