4. A 0.20 m long copper rod has constant velocity 0.30m/s traveling through a uniform magnetic field of 0.060 T . The rod, velocity, and magnetic field are all mutually perpendicular. What is the potential difference induced across the rod's length?
A) 0.0036 V
B) 0.040 V
C) 0.090 V
D) 1.0 V
E) 25 V