Question

. An electric dipole is held in an uniform electric field. Using suitable diagram, show that it doesn’t undergo any translatory motion, and (ii)Derive an expression for torque acting on it and specify its direction.

Answer 1

No translatory motion will occur in the dipole as all the clock wise motions and anti clock wise motions will cancel out each other, so there will be no rotatory motion. 

The direction of torque will be perpendicular to the direction of dipole. 
The expression of torque will be T = p x E sin0

Answer 2

Answer:

• The equation of torque becomes $T= p*M*Sin( \alpha)$

Explanation:

• There will be no translatory motion in the dipole because all clockwise and anticlockwise motions cancel each other out, hence there will be no rotatory motion.
• Torque is given by $T = F*t_{perpendicular}$.
  over here we can see that the dipole makes an angle $\alpha$ with the horizontal axis hence the perpendicular distance becomes
  $M*Sin (\alpha)$
• The equation of torque becomes
  $T= p*M*Sin( \alpha)$
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