Unit of Electric Field - Difference Between Electric Field and Magnetic Field

Edited By Team Careers360 | Updated on Jun 11, 2022 01:21 PM IST

This article includes the topics like definition of the electric field, the SI unit of the electric field, Coulomb’s law, superposition principle, the concept of the uniform electric field, and the difference between electric field and magnetic field.

In the year 1855, Michael Faraday presented the term electric field. The theory of field is then developed by Faraday in terms of the electric field.

What is an electric field?

A vector quantity present in every point in the space is called an electric field. It is the electrical property of charges. Mathematically, the electric field is the ratio of electric force F to the arbitrary charge q. It is given by,

E=F/q

According to the above formula, the force F acting on an arbitrary charge q shows the electric field at that particular point. The direction of the electric field depends on the direction of the force acting on the charge. Therefore, if the charge is positive, then the electric field points in the direction of the force that is away from the charge. If the charge is negative, then the electric field direction will be opposite of the force direction that is towards the charge.

Direction of electric field and force from the positive and negative charge

Figure 1 Direction of electric field and force from the positive and negative charge

Electric field strength: The intensity of the electric field is represented quantitatively by a factor called electric field strength. It doesn’t depend on the distance from the charged body.

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What is an electric field?
What is the unit of electric field?
What is the SI unit of electric field?
Difference between electric field and magnetic field:

Coulomb’s law:

In atoms, the force of attraction between the nucleus and electrons is due to the presence of the electric field. Hence, Coulomb stated the law and gave an equation for the force of attraction or repulsion between two point charges. It states that “The magnitude of the electrostatic force of attraction or repulsion is directly proportional to the product of the magnitude of charges and inversely proportional to the square of the distance between them.” The law is represented as,

F=Kq₁q₂/r²

Where F is the force, K is the Coulomb’s constant, q₁ and q₂ are the charges, r is the distance between the charges. In vector form,

$F=\frac{1}{4\pi \epsilon_0}\frac{qq_2}{r^2}\hat{r_i}$

Here, is the permittivity in free space, ri is the unit vector representing the distance between q and qi.

We know that the electric field is the force per unit charge. If we substitute the value of force from Coulomb’s law, then the expression for electric field is,

$\vec{E}=\frac{\vec{F}}{q}=\frac{1}{4\pi \epsilon_0}\frac{q_2}{r^2}\hat{r_i}$

In general, electric field

$K\frac{Q}{r^2}\hat{r}$

What is the unit of electric field?

The unit of the electric field is calculated by the ratio of a unit of force and unit of charge.

Unit of force is Newton

Unit of charge is Coulomb

Therefore, E= F/q=Newton/Coulomb

So, the unit of the electric field is Newton per coulomb, N/C

What is the SI unit of electric field?

According to the International System of Units, the unit of the electric field is kg.m.s-³A^-1

What is the si unit of electric field strength or electric field intensity?

Electric field strength measures the intensity of the electric field. The SI unit of electric field strength or electric intensity is volt per meter, V/m or V.m^-1

Uniform electric field:

If the electric field strength or field intensity is constant at all points then it is called a uniform electric field.

State the superposition principle of the electric field.

The superposition principle of electric field states that “Every charge in space creates an electric field at point independent of the presence of other charges in that medium. The resultant electric field is a vector sum of the electric field due to individual charges”.

The total force on a charge due to any number of point charges applied on it is determined by the superposition principle. The electric field doesn’t depend on the existence of other charges. It is applicable in the calculation of the net electric field, the net electric flux, and the potential energy.

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Write the formula for the electric field around a distributed charge, an isolated point charge, and multiple charges.

The electric field around a distributed charge is given by,

$\vec{E}= \frac{1}{4\pi \epsilon_0}\int\frac{dq}{r^2}\hat{r}$

The electric field around an isolated charge is given by,

$\vec{E}= \frac{1}{4\pi \epsilon_0}\frac{dq_i}{r^2}\hat{r_i}$

The electric field around multiple charges is given by,

$\vec{E}= \frac{1}{4\pi \epsilon_0}\sum_{i}^{}\frac{q_i}{r^2}\hat{r_i}$

In the above formulas, ϵ₀ is the permittivity in free space,

$\hat{r_i}$ is the unit vector representing the distance between the charges q and q_i.

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Difference between electric field and magnetic field:

Electric field and magnetic field can be differentiated as follows:

The electric field is the force experienced by the charged particles. The magnetic field is the area around a magnetic material in which the magnetic effect is observed.
The electric field is denoted by E and the magnetic field is denoted by B.
Electric field E is the force per unit charge, E=F/q and magnetic field B is the magnetic flux per unit area, B=∅/A
The unit of the electric field is Newton per coulomb or volt per meter whereas the unit of the magnetic field is Tesla.
Positive and negative charges are present in an electric field. The magnetic field consists of the north pole and south pole.
Electric field lines move towards the positive charge and away from the negative charge. While in magnetic field lines are produced at the north pole and ended at the south pole.
An electrometer is used to determine the electric field and a magnetometer is used to determine the magnetic field.

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