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
- Total Force on Point Charge from 2 Point Charges
- Total Force on Point Charge from Multiple Point Charges
- Results about electric charge can be found here.
Sources
- 1921: C.E. Weatherburn: Elementary Vector Analysis ... (previous) ... (next): Chapter $\text I$. Addition and Subtraction of Vectors. Centroids: Definitions: $1$. Scalar and vector quantities
- 1951: B. Hague: An Introduction to Vector Analysis (5th ed.) ... (previous) ... (next): Chapter $\text I$: Definitions. Elements of Vector Algebra: $1$. Scalar and Vector Quantities
- 1960: M.B. Glauert: Principles of Dynamics ... (previous) ... (next): Chapter $1$: Vector Algebra: $1.1$ Definition of a Vector
- 1969: J.C. Anderson, D.M. Hum, B.G. Neal and J.H. Whitelaw: Data and Formulae for Engineering Students (2nd ed.) ... (previous) ... (next): $1.$ Units and Abbreviations: $1.2$ SI units $(2)$ Derived units
- 1976: Ralph J. Smith: Circuits, Devices and Systems (3rd ed.) ... (next): Chapter $1$: Electrical Quantities: Introduction: Forces and Fields
- 1976: Ralph J. Smith: Circuits, Devices and Systems (3rd ed.) ... (previous) ... (next): Chapter $1$: Electrical Quantities: Definitions and Laws: Definitions: Table $1$-$2$: Important Derived Quantities
- 1990: I.S. Grant and W.R. Phillips: Electromagnetism (2nd ed.) ... (previous) ... (next): Chapter $1$: Force and energy in electrostatics: $1.1$ Electric Charge