Coulomb's Law
COULOMB’S LAW
INTRODUCTION
The magnitude of the force of attraction or repulsion between two electric charges at rest was studied by Charles Coulomb. He formulated a law, known as "COULOMB'S LAW".
STATEMENT According to Coulomb's law:
The electrostatic force of attraction or repulsion between two point charges is directly proportional to the product of charges.
The electrostatic force of attraction or repulsion between two point charges is inversely proportional to the square of distance between them.
MATHEMATICAL REPRESENTATION OF COULOMB'S LAW
Consider two point charges q1 and q2 placed at a distance of r from each other. Let the electrostatic force between them is F.
According to the first part of the law:
According to the second part of the law:
Combining above statements:
OR ---------------------(I)
Where k is the constant of proportionality.
VALUE OF K
Value of K is equal to 1/40 where o is permittivity of free space .Its volume is 8.85 x 10-12 c2/Nm2. Thus in S.I. system numerical value of K is 8.98755 x 109 Nm2c-2.
OTHER FORMS OF COULOMB'S LAW
Putting the value of K = 1/40 in equation (i)
FORCE IN THE PRESENCE OF DIELECTRIC MEDIUM
If the space between the charges is filled with a non conducting medium or an insulator called "dielectric", it is found that the dielectric reduces the electrostatic force as compared to free space by a factor (r) called DIELECTRIC CONSTANT. It is denoted by r . This factor is also known as RELATIVE PERMITTIVITY. It has different values for different dielectric materials. In the presence of a dielectric between two charges the Coulomb's law is expressed as:
VECTOR FORM OF COULOMB'S LAW
The magnitude as well as the direction of electrostatic force can be expressed by using Coulomb's law by vector equation:
Where is the force exerted by q1 on q2 and is the unit vector along the line joining the two
INTRODUCTION
The magnitude of the force of attraction or repulsion between two electric charges at rest was studied by Charles Coulomb. He formulated a law, known as "COULOMB'S LAW".
STATEMENT According to Coulomb's law:
The electrostatic force of attraction or repulsion between two point charges is directly proportional to the product of charges.
The electrostatic force of attraction or repulsion between two point charges is inversely proportional to the square of distance between them.
MATHEMATICAL REPRESENTATION OF COULOMB'S LAW
Consider two point charges q1 and q2 placed at a distance of r from each other. Let the electrostatic force between them is F.
According to the first part of the law:
According to the second part of the law:
Combining above statements:
OR ---------------------(I)
Where k is the constant of proportionality.
VALUE OF K
Value of K is equal to 1/40 where o is permittivity of free space .Its volume is 8.85 x 10-12 c2/Nm2. Thus in S.I. system numerical value of K is 8.98755 x 109 Nm2c-2.
OTHER FORMS OF COULOMB'S LAW
Putting the value of K = 1/40 in equation (i)
FORCE IN THE PRESENCE OF DIELECTRIC MEDIUM
If the space between the charges is filled with a non conducting medium or an insulator called "dielectric", it is found that the dielectric reduces the electrostatic force as compared to free space by a factor (r) called DIELECTRIC CONSTANT. It is denoted by r . This factor is also known as RELATIVE PERMITTIVITY. It has different values for different dielectric materials. In the presence of a dielectric between two charges the Coulomb's law is expressed as:
VECTOR FORM OF COULOMB'S LAW
The magnitude as well as the direction of electrostatic force can be expressed by using Coulomb's law by vector equation:
Where is the force exerted by q1 on q2 and is the unit vector along the line joining the two