Two charges `+3.2 xx 10^(-19) C` and `-3.2 xx 10^(-9) C` kept `2.4 Å` apart forms a dipole. If it is kept in uniform electric field of intensity `4 xx 10^(5) vol//m` then what will be its electrical energy in equilibrium ?

Options

A. `3 xx 10 ^(-23) J`
B. `- 3 xx 10 ^(-23) J`
C. `6 xx 10 ^(-23) J`
D. `-2 xx 10 ^(-23) J`

Answer

B

Explanation

Energy of dipole is
`U =- vecP . vecE =- PE cos theta`
`theta = 0` for stable equilibrium positoin
`implies U =- PE`
`implies U =`
`- (3.2 xx 10 ^(-19) xx 2.4 xx 10 ^(-10))(4 xx 10 ^(5))=- 3 xx 10 ^(-23) J`