In simple terms, Electrostatics is the study of static electric charges as opposed to the electric currents i.e it is the study of forces between the charges.
For example – In our daily lives, we might have encountered that when we rub a comb on dry hair and then bring it near torn small pieces of paper, the comb attracts those small bits of paper. In such a case, the comb is said to be electrically charged. This phenomenon arises from the force that electrically charged objects exert on each other, which is explained by Coulomb’s Law.
What is Electric Charge?
Electric charge is defined as the physical property of an object that causes it to experience a force when placed in an electromagnetic field i.e it is that quality of a matter with which it applies electrostatic force and interact with the surrounding objects. Electric Charge is often denoted by the symbol Q.
There are two types of Electric Charge
- Positive Charge- This is carried by Protons
- Negative Charge This is carried by Electrons
Characteristics of a Charge-
- Like charges repel and unlike charges attract each other
- Charge is conserved and it is quantized
How does Electrostatics work?
Electrostatics theory works when there a certain amount of charge builds up on the surface of an object due to contact with other surfaces. Although charge exchange happens whenever any two surfaces come in contact or are separate, the effects of this charge exchange are usually noticed when at least one of the surfaces has a high resistance to electrical flow. This happens because the charge transferred from one object to another is trapped there for quite a long time enough, for their effects to be observed.
As discussed earlier Electrostatic force is well explained by the Coulomb’s Law. This law states that the electrostatic force of attraction or repulsion between two charged bodies is directly proportional to the product of their charges and inversely as the square of the distance between the two bodies. The SI unit of a charge is the coulomb.
This law gives us the magnitude of the electrostatic force between two charges and is explained by the below given formula-
F = Kq1q2/r2
In the above formula, q1 and q2 are the charges, r is the distance between them, K is the constant here
K= 1/4πε0 = 9×109 Nm2C-2
Here ε0 = 8.85*10-12C2/N-mC2
Here this ε0 is the vacuum permittivity or permittivity of free space. Thus when the concept of permittivity of free space is used then the Coulomb’s law formula is-
F= 1/4πε0 q1q2/r2
Relative Permittivity (εr)
If there is any other medium other than air or vacuum in between the point charges then the Relative Permittivity of the medium is
εr = ε/ε0
Explanation of Coulomb force in vector form
According to Coulomb force if charge q1 exerts a force on charge q2 the latter charge i.e q2 also exerts an equal and opposite force on charge q1
Suppose if charge q1 exerts Force F12 on charge q2 then q2 also exerts equal and opposite Force F21 on charge q1
Here if r12 depicts the direction of force from charge q1 to charge q2 and r21 is the unit vector which depicts the direction of force from charge q2 to q1, then:
Here, we need to know the concept of Central forces which means that the forces due to two point charges are parallel to the line adjoining the point charges.
What is Electric Field?
The Electric field is the space surrounding the charge which exerts its influence on other charges. It is a vector field which can be defined anywhere except at the location of a point of charge. It is defined as the electrostatic force on a charge divided by the magnitude of the charge.
This means that the strength of the Electric field is measured by the electrostatic force it exerts on a unit positive charge.
Unit of Electric field is Newton per coulomb or volts per meter.
Every electric field has electric field lines which help in visualising the former. These lines begin with a positive charge and follow a path whether straight or curved and end on the negative charge.
Two electric field lines never intersect each other. Also, the number of lines drawn emerging from or terminating on a charge is proportional to the magnitude of the charge.
Electric Field Intensity
It is the electrostatic force acting on the positive charge on a point in an electric field. It is denoted by-
E= 1/4 πε0 Q/r2
Gauss’ law states that “the total electric flux through any closed surface in free space of any shape drawn in an electric field is proportional to the total electric charge enclosed by the surface.”
The total number of electrical field lines crossing an electrical field is called Electric Flux.
These were the basic concepts related to electrostatics. To know more about the related area, keep following TopprBytes.