Coulomb’s Law of Electrostatics physics Notes

Coulomb’s Law of Electrostatics

Electrostatic force of interaction acting between two stationary charges is given by
F = 1 / 4π εo q1q2 / r2

where q1, q2 are magnitude of point charges, r is the distance between them and εo is permittivity of free space.
Here, 1 / 4πεo = (10-7 N – s2 / C2)C2
Substituting value of c = 2.99792458 X 108 m/s,
We get 1 / 4πεo = 8.99 x 109N-m2/C2
In examples and problems we will often use the approximate value,
1 / 4πεo = 9 * 109N-m2/C2
The value of εo is 8.85 * 10-12 C2 / N-mC2.
If there is another medium between the point charges except air or vacuum, then εo is replaced by εoK or εoεr or ε.
where K or εr is called dielectric constant or relative permittivity of the medium.
K = εr = ε / εo
where, ε = permittivity of the medium.
For air or vacuum, K = 1
For water, K = 81
For metals, K = ∞
Electrostatic force of interaction acting between two stationary charges is given by
F = 1 / 4π εo q1q2 / r2

where q1, q2 are magnitude of point charges, r is the distance between them and εo is permittivity of free space.
Here, 1 / 4πεo = (10-7 N – s2 / C2)C2
Substituting value of c = 2.99792458 X 108 m/s,
We get 1 / 4πεo = 8.99 x 109N-m2/C2
In examples and problems we will often use the approximate value,
1 / 4πεo = 9 * 109N-m2/C2
The value of εo is 8.85 * 10-12 C2 / N-mC2.
If there is another medium between the point charges except air or vacuum, then εo is replaced by εoK or εoεr or ε.
where K or εr is called dielectric constant or relative permittivity of the medium.
K = εr = ε / εo
where, ε = permittivity of the medium.
For air or vacuum, K = 1
For water, K = 81

For metals, K = ∞