Electric Energy Density

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Electric Energy Density

“Energy density is a term used for the amount of energy stored in a given system or region of space per unit volume”

Energy density is a useful measurement when dealing with electric and magnetic fields. The idea is also used in nutritional research, though the calculation in this discipline is known as caloric density. The value is a useful parameter especially when comparing different fuels. For example, hydrogen fuel has lower energy density than gasoline. A higher energy density indicates that more energy can be stored or transported for the same amount of mass.

Energy density is a term used for the amount of energy stored in a given system or region of space per unit volume. Often only the useful or extractable energy is quantified, which is to say that chemically inaccessible energy such as rest mass energy is ignored. Quantified energy is energy that has some sort of, as the name suggests, quantified magnitude with related units.

Energy per unit volume has the same physical units as pressure, and in many circumstances is an exact synonym: for example, the energy density of the magnetic field may be expressed as (and behaves as) a physical pressure, and the energy required to compress a compressed gas a little more may be determined by multiplying the difference between the gas pressure and the pressure outside by the change in volume.

Definition of  electric energy density

  • Electric energy density is the amount of energy stored in a given system or region of space per unit volume or mass, though the latter is more accurately termed specific energy.
  • Energy density “D,” is given as:
  • D = E ÷ V, where
  • “E” is the total energy of the system
  • “V” is the volume of the system you are working with.

Example problem for energy density

In a certain region of space, the magnetic field has a value of 1.0 x 10-2T, and the electric field has a value of 2.0 x 106  VM-1 What is the combined energy density of the electric and magnetic fields? 

Answer: 

  • For the electric field, the energy density is 
  • For the magnetic field, the energy density is 
  • The net energy density is the sum of the energy density due to the electric field and the energy density due to the magnetic field: 

Points to Remember

  • Electric energy density is the amount of energy stored in a given system or region of space per unit volume or mass
  • Energy density “D,” is given as:
  • D = E ÷ V, where
  • “E” is the total energy of the system
  • “V” is the volume of the system you are working with.
  • For the electric field, the energy density is WE =0.5?0E2.
  • For the magnetic field, the energy density is  WB= 0.5*B 2./ µ0

For the electric field the energy density is

For the magnetic field the energy density is

Other types of Electric energy