# What is Electric Field?

Posted by Sibasish Ghosh on 24/2/2012 & Updated on 8/8/2018**electric field**of former charge.

**Electric field**is also known as

**electrostatic field intensity**.

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Hence, we can say, if a charge is a positive charge, then the lines of force come out of this charge. But for a negative charge, these lines of force come into this charge.

When a charged particle enters the electric field of another charged particle, it experiences a force as per Coulomb’s law. In other words,** electric field** is the region around a charged particle where another charge can feel the lines of force by getting repulsed or attracted as per their sign of charge.
Let us take a charge, Q_{1} Coulomb. Let us imagine one positive unit charge placed r meter away from the centre of Q_{1}.

So, as per Coulomb's law, the force experienced by the unit positive charge is,
Here, we considered that the medium is air or vacuum in which we placed both charge Q_{1} and positive unit charge. The force experienced by the unit positive charge is the measurement of the electric field of Q_{1} at the point where a positive unit charge gets placed.
Now, we place a charge Q_{2} at same point where, unit positive charge was placed.
Two positive charge particles repel each other, two negative charges repel each other and two opposite charge particles attract each other with force .

This attraction or repulsion force must be within the **electric field**.
This electric field is denoted by . So, the vector of electric field , denotes how strongly an electric charge is repulsed or attracted by the charge which creates the electric field.

## What is the direction of electric field?

Electrostatic-force between two electrical charges is either repulsive or attractive depending upon the nature of charges, hence it is a vector quantity. So, an electric field is a vector quantity, since an electric field is a force per unit positive charge, so the direction of the electrostatic field must follow the direction of the electrostatic force. When we place a unit positive charge in an electric field, it either comes closer or goes far, depending upon the nature of the charge, by which the field is created. The direction of the electric field is given by the direction of motion of the unit positive charge. Electric Field Intensity is always perpendicular to the surface. As per figure, two elementary surface areas () are considered, named A and B. So number of lines of force through A is equal to the number of lines of force through B. Now we can calculate,## Properties of Electric Field Lines

Electric field Lines are two types.- Uniform
- Non uniform

- Electric field lines of force have a tendency to get separated from each other in the direction perpendicular to their lengths. They repel if they are of like charges.
- Electric lines of force start from the positively charged surface of a body and end negatively charged surface of a body.
- These lines of force are like elastic string, they comes to contract in length i.e. attract each other with respect to the opposite charges.
- Closeness of lines of forces symbolizes more strength of electric field and vice versa.
- Parallel lines indicate uniform field.
- Two lines of forces never intersect each other.
- Lines of force never pass through a conductor, i.e. field inside a conductor is always zero.
- The tangential direction at any point on the lines of forces indicates the direction of the force acting on the positive charge at that point.

## What is the Value of Electric Field Outside a Solid Spherical Charged Conductor?

Let us consider a uniformly charged solid sphere of radius r. Consider a point P at a distance R from centre of the sphere (R > r). Now Total surface of the sphere is dS= 4ᴫR^{2}, Applying Gauss’s Law, Electric flux lines

## What is the Value of Electric Field Due to Line Charge?

Consider an infinitely straight conductor that is thin and placed vertically. Suppose the total length of the wire is L, and the total charge is q, then line charge density is l/q = λ. Gaussian Surface dS = 2ᴫrl. Let,**Electric field**intensity electric field is to be calculated at point P. Applying Gauss’s Law, Electric flux lines Keep it in your mind that for a point charge,