Here's the textbook question: Twelve wires of equal length 'l' are connected to form a skeleton cube which moves with constant velocity v perpendicular to the magnetic field B. What will be the induced emf in each arm of the cube?
As per my understanding, motional emf is produced in a conductor that moves in a direction perpendicular to the magnetic field. Hence, each arm should develop a motional emf.
The book says - "Emf is produced only in the arms that are perpendicular to both $V$ & $B$. Thus, only EH, FG, AD, BC produce a motional emf, $\epsilon= BLV$ "