When the metal rod moves through the magnetic field, the free electrons inside it are forced to move along with it.

Moving charges in a magnetic field experience a Lorentz Force. We can find the direction of this force using the Right Hand Push Rule:

• Point your fingers in the direction of the Magnetic Field (B) — either into the screen (✕) or out of the screen (●).
• Point your thumb in the direction the rod is moving (v).
• Your palm now faces the direction of the force on a positive charge.

Because electrons have a negative charge, they experience a force in the opposite direction (pushing out from the back of your hand).

This force pushes the electrons to one end of the rod, leaving the other end with a net positive charge. This charge separation creates an internal Electric Field (E) and an induced Motional EMF!