  We report on the electrically driven rotation of $2.4~\mu$m-radius, optically
levitated dielectric microspheres. Electric fields are used to apply torques to
a microsphere's permanent electric dipole moment, while angular displacement is
measured by detecting the change in polarization state of light transmitted
through the microsphere (MS). This technique enables greater control than
previously achieved with purely optical means because the direction and
magnitude of the electric torque can be set arbitrarily. We measure the
spin-down of a microsphere released from a rotating electric field, the
harmonic motion of the dipole relative to the instantaneous direction of the
field, and the phase lag between the driving electric field and the dipole
moment of the MS due to drag from residual gas. We also observe the gyroscopic
precession of the MS when the axis of rotation of the driving field and the
angular momentum of the microsphere are orthogonal. These observations are in
quantitative agreement with the equation of motion. The control offered by the
electrical drive enables precise measurements of microsphere properties and
torque as well as a method for addressing the direction of angular momentum for
an optically levitated particle.
