Figure shows a metal rod PQ resting on the rails AB and positioned between the poles of a permanent magnet. The rails, the rod and the magnetic field are in three mutual perpendicular directions. A galvanometer G connects the rails through a switch K. Length of the rod = 15 cm, B = 0.50 T, resistance of the closed loop containing the rod = 180.0 $m\Omega$. Assume the field to be uniform.
The induced emf produced in the moving rod if the magnetic field becomes parallel to the rails instead of being perpendicular will be:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Zero
The induced emf is,
$ε=Blv\sin θ$
$θ$ = Angle between the magnetic field and velocity of the rod.
and,
if the magnetic field becomes parallel to the rails, $θ$ become 0°.
$∴ε=Blv\sin 0°$
$=0$