# OHM's Law

## Quick Reference

### Ohm's Law Calculations

`V = I * R`

R = V / I

I = V / R

### Power Triangle

## More Info

The amount of current flowing through a conductor is proportional to the voltage applied across the conductor. This is true of all conductors with the exception of super-conductors. Mathematically this is stated as:

`V = k * I`

Where:

`V`

is the voltage (in volts) drop across the conductor.`I`

(for*Intensity*), the current (in amps) flowing through the conductor.`k`

is the constant of proportionality.

### Ohm's Law

This relation is codified in *Ohm's Law*, where, `k`

is replaced by resistance (in ohms) of the conductor. The equation becomes:

`V = I * R`

For historical reasons, amperage is often labeled `I`

(for intensity), and sometimes voltage is labeled `E`

(for electromotive force). So, while the most common labeling for Ohm's law is typically uses `V`

for volts, `I`

for amps, and `R`

for resistance, sometimes the following is seen:

`E = I * R`

Where `E`

is voltage.

### Other Forms of Ohm's Law

Using algebra, Ohm's law can also be solved for resistance (`R`

) or (`I`

):

#### Solved for Resistance (R)

`R = V / I`

ohms = volts / amps

#### Solved for Voltage (V)

`I = V / R`

amps = volts / ohms

### Ohm's Law Pyramid

The *Ohm's Law triangle*, also known as the *power triangle* is helpful in remembering the various solutions of Ohm's law:

It roughly represents the mathematical relationship of Ohm's law; it's divided vertically by a line that indicates division (below `V`

), and horizontally, with a line that stands for multiplication (between `I`

and `R`

).

To read it, choose any given unit as the solution, and then use the division/multiplication rules of the lines.

Therefore, starting with a solution for `V`

, it's read as:

`V = I * R`

## Further Reading

For a more in-depth discussion about Ohm's law and resistance, check out Part 4 of the Electronics Tutorial.