The figure shows an apparatus suggested by Faraday to generate electric current from a flowing river. Two identical conducting plates of length $a$ and width $b$ are placed parallel facing one another on opposite sides of the river flowing with velocity $u$ at a distance $d$ apart. Now both the plates are connected by a load resistance $R$. Then the current through the load $R$ is: (Consider the vertical component of the magnetic field produced by the earth is $B_v$ and the resistivity of river water is $\rho$.)

• A
  $\frac{B_v ub}{R}$
• B
  $\frac{B_v ud}{R + \frac{\rho d}{ab}}$
• C
  $\frac{B_v ud}{R + \frac{\rho d}{ab}}$
• D
  None