# Definition:Electric Charge/Quantum

## Definition

Electric charge has been demonstrated to be quantized.

The quantum of electric charge is the elementary charge $\E$:

 $\ds \E$ $=$ $\ds 1 \cdotp 60217 \, 6634 \times 10^{−19}$ coulombs exactly (by definition) $\quad$ This sequence is A081823 in the On-Line Encyclopedia of Integer Sequences (N. J. A. Sloane (Ed.), 2008). $\ds$ $=$ $\ds 1 \cdotp 60217 \, 6634 \times 10^{−20}$ abcoulombs $\quad$ This sequence is A081823 in the On-Line Encyclopedia of Integer Sequences (N. J. A. Sloane (Ed.), 2008). $\ds$ $=$ $\ds 4 \cdotp 80320 \, 425(10) \times 10^{-10}$ statcoulombs

This is so small that to all practical purposes in everyday measurement of electricity, it can be treated as though it were continuous.

### Symbol

The symbol used to denote the elementary charge is usually $\E$ or $e$.

The preferred symbol on $\mathsf{Pr} \infty \mathsf{fWiki}$ is $\E$.

## Examples

### $60 \ \mathrm W$ Bulb at $200 \ \mathrm V$

Consider a $60 \ \mathrm W$ light bulb running at $200 \ \mathrm V$.

Approximately $2 \times 10^{18}$ units of elementary charge flow along the filament of the light bulb every second.

## Historical Note

Until the $2019$ definition of the elementary charge as exactly $\E = 1.60217 \, 6634 \times 10^{−19} \, \mathrm C$, it was the subject of measurement.

This measurement has been accomplished to greater and greater accuracy over time.

By $1964$, it was established as:

$\E = 1 \cdotp 60219 \, 17 \pm 0 \cdotp 00000 \, 70 \times 10^{−19} \, \mathrm C$

## Technical Note

The $\LaTeX$ code for $\E$ is \E .

## Sources

which gives the mantissas of these figures as:
$1 \cdotp 602 \, 191 \, 7$ with an uncertainty of $\pm 70$ corresponding to the $2$ least significant figures
$4 \cdotp 803 \, 250$ with an uncertainty of $\pm 21$ corresponding to the $2$ least significant figures