A \( 20 \, \text{m} \) long uniform copper wire held horizontally is allowed to fall under the gravity \( (g = 10 \, \text{m/s}^{2}) \) through a uniform horizontal magnetic field of \( 0.5 \, \text{Gauss} \) perpendicular to the length of the wire. The induced EMF across the wire when it travels a vertical distance of \( 200 \, \text{m} \) is ______ mV.
