# Definition:Electric Charge

## Definition

Electric charge is a physical quantity of matter which causes it to experience a force when near other electrically charged matter.

It is a scalar quantity.

It has been discovered by experiment that the corresponding force depends on the magnitudes of those electric charges, their displacements from each other, and their velocities.

### Quantum

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 usual symbol used to denote the electric charge on a body is $q$.

### Dimension

The dimension of measurement of electric charge is $\mathsf {I T}$.

### Units

The SI unit of electric charge is the coulomb $\mathrm C$.

In the CGS unrationalised electromagnetic system, the base unit of electric charge is the abcoulomb $\mathrm {abC}$.

In the CGS unrationalised electrostatic system, the base unit of electric charge is the statcoulomb $\mathrm {statC}$.

### Conversion Factors

 $\ds$  $\ds 1$ coulomb $\ds \text {corresponds to}$  $\ds 10^{-1}$ abcoulomb (or e.m.u. of electric charge) $\ds \text {corresponds to (approximately)}$  $\ds 3 \times 10^9$ statcoulomb (or e.s.u., or franklin)

## Polarity

The polarity of an electric charge can be one of $2$ types:

### Positive Electric Charge

A positive electric charge is an electric charge which is of the same polarity as the electric charge on a proton.

When it is necessary to assign a value to a positive electric charge, a $+$ (plus) sign is used, and the value assigned is a positive number.

### Negative Electric Charge

A negative electric charge is an electric charge which is of the same polarity as the electric charge on an electron.

When it is necessary to assign a value to a negative electric charge, a $-$ (minus) sign is used, and the value assigned is a negative number.

## Neutral

A body which has no electric charge on it is described as (electrically) neutral.

## Also see

• Results about electric charge can be found here.