Charge Density Formula

Charge Density Formula

The charge density formula is one of the most important formulas for calculating electric fields and potentials. It can be applied to any point in space and can be used to find the electric field or potential due to multiple charges located at any point in space. 

About the Topic 

When we talk about “charge density,” we’re referring to the amount of electrical charges contained in a certain space.

For example, if you have a device that can move electrons between two points in an electric field, charge density is the total number of electrons per unit volume at any given point.

Charge density isn’t a physical property of matter, but rather a calculation based on the number of subatomic particles moving in a particular space.

In physics, charge density is the amount of electric charge per volume of space. It is used to describe how much electric charge exists in a specific volume of space, for example, how many electrons or protons are in a given volume.

The SI unit of charge density is coulomb per cubic metre (C/m3).

Formula

Linear charge density is computed as:

λ= q/l

Surface charge density is computed as:

σ= q/A

Volume charge density is computed as:

ρ= q/V

Where, 

λ- Linear Charge Density

σ- Surface Charge Density

ρ- Volume Charge Density

A- Area

L- Length

V- Volume

Solved Examples

• Find the charge density if a charge of 8 C is present in a cube of 4 m3.

Given :

Charge q = 8 C

Volume v = 4 m3

The charge density formula is given by

ρ = q / v

= 8 / 4

Charge density ρ = 2 C/m3

• Determine the charge density of an electric field, if a charge of 6 C per metre is present in a cube of volume 3 m3.

Given parameters are as follows:

Electric Charge, q = 6 C per m

The volume of the cube, V = 3m3

The charge density formula computed for volume is given by:

ρ = q / v

ρ= 6/3

Charge Density Formula is ρ= 2C/m3.