Energy Density Formula

Definition of Energy Density

Energy density is the amount of energy contained in a given system or region of space per unit volume that can be obtained from a given volume of substance or material.

For instance, the calories per gram of food. Foodstuffs that have low energy density provide less energy per gram of food which means that you can eat more of them since there are fewer calories.

It is denoted by letter U.

Magnetic and electric fields also store energy.

Formula 

In case of electric field or capacitor, the energy density formula is given by,

Where,

• E=E is the electric field 

• ε0=permittivity of free space

The energy density formula in case of magnetic field or inductor is given by,

 

where, 

•  B=Magnetic field 

•  μ0 =permeability of free space

Thus, the expression for energy density is equal to the summation of the energy density of the electric field and the magnetic field.

Solved Example

Example: Calculate the energy density of a capacitor, if its electric field,  E = 5 V/m.

Solution:

Given,

E = 5V/m

We know that,

ϵ0 = 8.8541× 10−12F/m

The formula of the capacitor is given by

 

 

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