Question

Electric force between two stationary charges becomes 1/10 when space between
them is filled by a dielectric medium. Relative permittivity of the medium is:
(A) 1
(B) 10
(C) 100
(D) 1.1
​

Answer 1

Suppos,

permittivity of air = ę

permittivity of medium = é

Relative permittivity (K) = é/ę

• Formula Derivation :

Force act in air = Fo = q^2/4pi ę r^2

Force act in medium = Fm = q^2/4pi é r^2

Take ratio of Fo/Fm = é/ę = K

so, Fo/Fm = K

• Given :

Fm = Fo / 10

• Calculation :

K = Fo / Fm = 10

• Answer :

Relative permittivity of medium = 10