## Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)

$\tau = p~E$
We can find the torque about the center due to the electric field $E$ acting on the $+q$ charge: $\tau = (q)~(E)~(\frac{s}{2})$ $\tau = \frac{q~s~E}{2}$ By the right hand rule, this torque is into the page. We can find the torque about the center due to the electric field $E$ acting on the $-q$ charge: $\tau = (q)~(E)~(\frac{s}{2})$ $\tau = \frac{q~s~E}{2}$ By the right hand rule, this torque is into the page. We can find the magnitude of the net torque: $\tau = \frac{q~s~E}{2}+\frac{q~s~E}{2}$ $\tau = qs ~E$ $\tau = p~E$