A dipole is placed parallel to the electric field. If W is the work done in rotating the dipole by 60° then work done in rotating it by 180° is

Options

A. 2W
B. 3W
C. 4W
D. `W//2`

Answer

C

Explanation

If dipole be rotated from an initial orientation `1theta=theta_(1)` to
final orientation `1theta=theta_(2)`, the total work required is
`W=int_(theta)^(theta_(2))pE sinthetad theta=pE[-costheta]_(theta_(1))^(theta_(2))`
where , p is dipole moment and E the electric field . Case 1
`W=pE[1-cos60^(@))=pE(1-(1)/(2))=(pE)/(2)rArrpE=2W`
Case II `W_(2)=pE(1-cos180^(@))=2W(1+1)=4W`