At a place,the value of the horizontal component of the Earth's magnetic field $H$ is $3 \times 10^{-5} \, Wb/m^2$. $A$ metallic rod $AB$ of length $2 \, m$,placed in the east-west direction with end $A$ towards the east,falls vertically downward with a constant velocity of $50 \, m/s$. Which end of the rod becomes positively charged,and what is the value of the induced potential difference between the two ends?

• A
  End $A$,$3 \times 10^{-3} \, mV$
• B
  End $A$,$3 \, mV$
• C
  End $B$,$3 \times 10^{-3} \, mV$
• D
  End $B$,$3 \, mV$