# Electronics Toolbox

## Ohm's Law Calculator

Enter two values in the form fields below to calculate the third value.

### Understanding Ohm's Law

Ohm's Law states that the current $$I$$ passing through a conductor between two points is directly proportional to the voltage $$V$$ across the two points and inversely proportional to the resistance $$R$$ of the conductor. This relationship can be expressed by the formula:

##### $$V = IR$$

where:

• $$V$$ is the voltage across the conductor (in volts, V),
• $$I$$ is the current flowing through the conductor (in amperes, A),
• $$R$$ is the resistance of the conductor (in ohms, Ω).

#### Using Ohm's Law

Ohm's Law can be used to calculate the voltage, current, or resistance in a circuit if the other two quantities are known. It’s rearranged as follows depending on what you need to find:

• To find the current $$I$$:
##### $$I = \frac{V}{R}$$
• To find the voltage $$V$$:
##### $$V = IR$$
• To find the resistance $$R$$:

#### Example

Suppose you have a resistor with a resistance of 200 ohms, and a current of 2 amperes is flowing through it. To find the voltage across the resistor, you would use Ohm’s Law:

$$V = IR = 2\, A \times 200\, \Omega = 400\, V$$

#### Practical Application

Ohm's Law is essential for designing and analyzing electrical and electronic circuits. It helps in determining the appropriate values of resistors to use for a desired current flow under a given voltage. It's also fundamental in troubleshooting circuits to find unknown values when others are known.

#### Visual Representation

Think of Ohm's Law as a balance scale where voltage $$V$$ is on one side, and the product of current $$I$$ and resistance $$R$$ is on the other. They must balance for the circuit to function correctly.

#### Key Points

• Direct Proportionality: Voltage is directly proportional to the product of current and resistance.
• Fundamental Rule: It applies to any part of an electrical circuit, any component, or any group of components.
• Unit Consistency: Ensures the units of volts, amperes, and ohms are consistently applied and calculated.