I would like to ask a question regarding electric charge. I see that charge has $2$ units.

  1. Elementary charge
  2. Coulomb

For example A proton has a charge of $+1e$ or of $+1.602 * 10^{-19}$ Coulombs.

But there is another way but I don't have the name of the expression way or method. I see people say a proton has a charge that of +1 ( within out any unit). This is a way I assume is originated from the elementary under t but I don't know what's the name. I would be grateful if someone could help me.


closed as unclear what you're asking by Jan, Todd Minehardt, ringo, M.A.R., getafix Nov 2 '16 at 5:26

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  • 1
    $\begingroup$ Simply if you talk about particles it's obvious that you're using elementary charges and there's no need to write "e" What's here to ask about? $\endgroup$ – Mithoron Nov 1 '16 at 12:02

There are 3 units that are used to express charge.

  • Coulomb (C)

This is most commonly used in macroscopic situations.

1 coulomb of charge is that which, if placed at a separation of 1 metre from another charge of magnitude 1 coulomb, experiences a force of $8.99\times 10^9$N along the line joining the charges.

This definition results from the observation-based Coulomb's Law of Electrostatic Forces: $F_e=k_e\frac{q_1 q_2}{r^2}$

  • e

This is a unit of charge most commonly used in microscopic situations due to its convenience.

It is the magnitude of charge present on 1 electron, or 1 proton - it is equal in magnitude.

$e\approx 1.602\times 10^{-19}$

  • Electrostatic unit of charge (esu)

The least used of the three, it is the CGS unit of charge. It is also known as franklin (Fr), or statcoulomb (statC).

1 esu of charge is that which, if placed at a separation of 1 centimetre from another charge of magnitude 1 esu, experiences a force of magnitude 1 dyne along the line joining the two charges.

Again, from Coulomb's Law of Electrostatic Forces, we can determine that

$1 esu\approx 3.335\times 10^{-10} C$

  • $\begingroup$ Oh my god thank you. Now I know one more unit (which is 1 esu). I would like to ask in terms of why sometimes people use: a proton has "a charge of $+1e$" and if this kind of expressions has a label for it !? $\endgroup$ – PandoraU.U.D Nov 1 '16 at 4:34

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