# Stored Electricity: Voltage and Volts ($V$)

Stored electricity is called voltage and is measured in volts. More precisely, **voltage** is the difference in electric potential energy between two points.

One **volt** is equal to 1 joule ($J$, see physics) per 1 coulomb ($C$), or $V = \frac{J}{C}$. A **coulomb** is a quantity of electrical charge (i.e. electrons or protons). Volts can also be expressed in terms of watts and amps: $V=W/A$.

Another way to put it is, a volt is the amount of electricity required to accelerate 1kg by 1 meter per second squared (a joule) for 1 second (resulting in a displacement of $1m$), divided by the quantity of electrical charges (coulombs). In other words, a volt is "how much work can be done per coulomb".

Voltage can be derived by Ohm's Law as $V = IR$.

## Common Voltages

Source | Voltage |
---|---|

AA Battery | $1.5V$ |

Car battery | $12V$ |

Wall socket | $110V$ or $220V$ |

## Video: Voltage (Khan Academy)

## History

Volts and voltage are both named after Alessandro Volta, who invented the first battery in 1800.

## Deeper Knowledge on Voltage and Volts

### Conductance and Siemens

The ability to conduct to current, measured in siemens

### Ohm's Law

A formula for determining voltage, current, and resistance

### Resistance and Ohms

Opposition to current, measured in ohms

### Watt's Law (Power Law)

A formula to define the relationship between power, voltage, and current (P=IV)

## Broader Topics Related to Voltage and Volts

### Charge and Coulombs

How force is exerted in electromagnetic field, measured in coulombs

### Electrical Engineering

Build and deconstruct electrically powered devices

### Electricity

Energy that results from charged particles

### International System of Units (SI)

Formal terms and definitions of the metric system