The field or space around a charge particle where its force can be experienced by any other charged particle is called the electric field of former charge. Electric field is also known as electrostatic field intensity.
If a unit positive charge is placed near a positive charge, the unit positive charge will experience a repulsive force, due to which the unit positive charge will move away from the said charge. The imaginary line through which the unit positive charge moves, is known as line of force. Similarly, if a unit positive charge placed in the field of negative electric charge, the unit positive charge will experience an attractive force, due to which the unit positive charge will come closer to the said negative charge. In that case, line through which the positive unit charge moves, also known as line of force.
Hence, we can say, if a charge is 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 charge particle enters the electric field of another charge particle it experiences a force as per Coulomb’s law. In other word, electric field is the region around a charge particle where the lines of force can be felt by another charge by getting repulsed or attracted as per their sign of charge.
Let us take a charge, Q1 Coulomb. Let us imagine one-unit positive charge placed r meter away from the center of Q1.
So, as per Coulomb’s law the force experienced by the unit positive charge is,
Here, we considered that the medium in which both charge Q1 and unit positive charge are placed is air or vacuum. The force experienced by the unit positive charge is measurement of electric field of Q1 at the point where unit positive unit charge is placed.
Now, we place a charge Q2 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.
Video on 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, electric field is a vector quantity, since electric field is the force per unit positive charge, so the direction of electrostatic field must follow the direction of 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.
- Non uniform
But for each type always follows some important mannerism as their characteristics or properties. They are-
- 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 center of the sphere (R > r). Now Total surface of the sphere is dS= 4ᴫR2 , Applying Gauss’s Law, Electric flux lines
What is the Value of Electric Field Due to Line Charge?
Consider a infinitely straight conductor that is thin and placed vertically. Suppose total length of the wire is L and 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,
1.Bunty B. Bommera
2.Dakshata U. Kamble