an electric dipole is formed by 2 particles fixed at the end of a light rod of length l...the mass of each particle is m and the charges are +q and -q...the system is placed in such a way that the dipole axis is parallel to a uniformelectric field E that exists in the region..the dipole is slightly rotated about its center and released..show that for small angular displacement motion is SHM..Evaluate its time period!

Question

anonymous · Answer

torque, T=-lqEsin(x) , where x is the small angle through which dipole is rotated.

for small x, sin(x)=x

so, we get  T=-IqEx

since T is directly proportional to x so it is excuting SHM.

and its time period is 2*(pi)*(I/(lqE))^(1/2)

anonymous · Answer

why torque has a negative sign...??

anonymous · Answer

the negative sigh shows that as theta increases the torque acts in the opposite direction.