  We present for the first time an experimental investigation of
electrohydrodynamic (EHD) flows within a neutrally buoyant drop with initial
radius of 2.25 mm. Utilizing particle image velocimetry (PIV) and high-speed
shadowgraphy, we measure the internal circulation and reported velocity
profiles in the bulk and at the interface of the drop. Two leaky dielectric
liquids, Silicone and Castor oils, are employed as the drop and external phase,
allowing for the analysis of two shape configurations: oblate and prolate. The
strength of the applied uniform electric field, $E_o$, spans from 0.125 to 1.75
kV/cm, enabling the analysis covering the small-deformation limit, where the
leaky dielectric model (LDM) is applicable. Drops with larger deformations, for
which no analytical velocity field is available, are also investigated. Our
measurements show a good agreement with the LDM theory for the
small-deformation cases. The flows begin at the interface as a result of jump
in the electric stresses, leading then to four counter-rotating vortices inside
the drop. At permanent regime, the analytical solutions adequately predicts the
radial and tangential velocity components both in the bulk and at the interface
of the drop. However, a nuanced behavior is noticed for larger deformations,
where the LDM theory underpredicts the internal circulation. Moreover, due to
the increased deformation, a non-uniform azimuthal profile is observed for the
velocity at the interface. Transient measurements of this velocity component
enlighten the dynamic response of the EHD flows of the drop. Following the
currently available analytical solutions, the dynamic response is governed by
the time-scale of its deformation. We propose a critical value of electric
capillary number of roughly 0.1 below which the LDM adequately describes the
velocity field in both quasi steady-state and transitory regimes.
