Question

A force F acts between sodium and chlorine ions of salt (sodium chloride) when put 1 cm apart in air. The permittivity of air and dielectric constant of water are `epsilon_0` and K respectively. When a piece of salt is put in water, electrical force acting between sodium and chlorine ions 1 cm apart is ____________.

Options

• `"F"/"K"`

• `"FK"/epsilon_0`

• `"F"/("K"epsilon_0)`

• `("F"epsilon_0)/"K"`

Answer 1

A force F acts between sodium and chlorine ions of salt (sodium chloride) when put 1 cm apart in air. The permittivity of air and dielectric constant of water are `epsilon_0` and K respectively. When a piece of salt is put in water, electrical force acting between sodium and chlorine ions 1 cm apart is `"F"/"K"`.

Explanation:

`"F" = 1/(4 piepsilon_0"K") ("q"_1 "q"_2)/"r"^2`

`therefore "F" prop 1/"K"`

For air K= 1

Let F' be electrical force when placed in water

`therefore "f'"/"f" = 1/"K"`

`therefore "F'" = "F"/"K"`