Figure shows a rectangular conductor PQRS in which the conductor PQ is free to move. The conductor PQ is moved towards the left with a constant velocity V as shown in the figure. Assume that there is no loss of energy due to friction. What will be the magnetic flux linked with the loop PQRS and the motional emf? |
Magnetic flux = $Bl(xV)$; Motional emf = $Blx$ Magnetic flux = $Blx$; Motional emf = $(BlV)/t$ Magnetic flux = $Blx$; Motional emf = $BIV$ Magnetic flux = $B/(lx)$; Motional emf = $BlV$ |
Magnetic flux = $Blx$; Motional emf = $BIV$ |
The correct answer is Option (3) → Magnetic flux = $Blx$; Motional emf = $BIV$ Magnetic flux linked with loop PQRS: The flux through the loop = magnetic field × area (field is uniform and perpendicular to plane). Area = length of side PR (call it $l$) × horizontal separation $x$ (between PQ and the opposite side). $\Phi = B\,l\,x$ Motional emf induced in the moving rod PQ: For a rod of length $l$ moving with velocity $V$ perpendicular to a magnetic field $B$, the motional emf is $\mathcal{E} = B\,l\,V$ Therefore: Magnetic flux = $B l x$; Motional emf = $B l V$ |