Definition:Electric Charge/Quantum

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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
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