A metallic cube of side $15 \mathrm{~cm}$ moving along $y$-axis at a uniform velocity of $2 \mathrm{~ms}^{-1}$. In a region of uniform magnetic field of magnitude $0.5 \mathrm{~T}$ directed along $z$-axis. In equilibrium the potential difference between the faces of higher and lower potential developed because of the motion through the field will be _________ mV.