# What is Electric Field Intensity? Formula, Unit

In the properties of electric charge we have learned that an electric charge produces electric field and magnetic field around it. Now, what is an electric field and its intensity? What is the formula for the electric field intensity? In this article, we are going to learn the electric field and electric field intensity and the formula for electric field intensity.

Contents in the article:

• Electric Field
• Definition of Electric Field
• Formula of Electric Field Intensity
• Force on a charge placed in external electric field
• Unit of Electric Field Intensity
• Dimension of Electric Field Intensity

## What is theElectric Field?

Electric Field is the region around a charge inside which the charge can interact with other charges. If the electric field is due to a positive charge then it will attract other positive charges and repels other negative charges within this region. This region is a spherical region for a point charge.

## What isElectric Field Intensity?

Electric Field Intensity is the strength of the electric field at any point inside the electric field region. Electric field Intensity at a point inside the electric field is defined as the electric force on an one coulomb positive charge placed at that point. So, it is nothing but the electric force per unit positive charge. It is denoted as the letter E. Some authors write electric field intensity as the Electric field. But these two terms are conceptually different.

If a positive Q charge produces an electric field E around it, then the electric force on a positive q charge in this electric field region is F = qE. Electric field Intensity (E) is a vector quantity that has the same direction as that of the electric force.

## Formula of Electric Field Intensity

One can determine the expression or formula for the electric field intensity directly from the Coulomb’s Law or by applying Gauss’s law of electrostatics.

The formula for electric field intensity (E) at r distance from a positive Q charge is E= k Q/r2 ….(1)

where k is coulomb constant.

In SI system k = 9 * 109 and in CGS system, K =1.

Again, the relation between electric field and electric force is F=qE.

## What is the Unit of electric field intensity?

One can determine the unit of electric field intensity from the equation, F=qE or, E=F/q

We know that the SI unit of force is Newton (N) and the SI unit of charge is Coulomb (C). So,

SI unit of electric field Intensity is N/C. It has another SI unit as Volt/metre (V/m).

CGS unit of electric field Intensity is dyn/statC or dyn/esu.

## Dimension of E

Dimension of force is [ MLT-2 ] and the dimension of electric charge is [ TI ]. So, the dimensional formula of the electric field intensity is [ MLT-3I-1 ].

## Difference between electric field and electric field intensity

The electric field is the region around a charge inside which it can interact with other charges. But the electric field intensity gives the strength of the electric field at any certain point. Electric field intensity is actually the electric force on a unit positive charge placed inside the electric field. In higher education, the term electric field itself represents the electric field intensity. Because, there is no applications of the region around the charge. But the strength of that region has the importance.

## Numerical problems on electric field

1. What will be the electric field at a point at 10 cm distance from a +5 C charge? If we place another +2 C charge at that point, what will be the electrostatic force on +2 C charge?

Hints: Use equation-(1) to find electric field and use Coulomb’s law to find electrostatic force.

This is all from this article. If you have any doubt on this topic you can ask me in the comment section. You also can visit my website to see other posts related to Electronics and Physics.

Thank you!

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