Motional Emf
The emf induced by the motion of conductor across the magnatic field is called motional emf.
Explanation
Consider a rod of length ‘’L’’ placed between two matel rails saprated by the distance of L. A galvanometer is connected between c and d. This forms a complete abcd as show in fig.
When rod is pulled towards right with velocity v, the galvanometer shows that current is flowing through loop. The rod acts as a source of emf.
E = Vb –Va = ΔV
We know that force experience by the charge moving perpandicular to the magnatic field is given by
F = q(V x B)
F= qVBSinѲ
F = qVB (Ѳ = 90)
According to right hand rule the direction of force is from a to b. The current is flowing anticlock wise. After some times the concentration of charges at the top increase and deficiency occurs at bottom.
The electric field will be set up from top to bottom. The electric field exert a force on the charge.
The electric field will be set up from top to bottom. The electric field exert a force on the charge.
At equilibrium
Fe = Fb
qE = qVB
E = VB ____ (1)
As we know that electric field intensity is equal to the negative of potential gradient . So
E = - Δv/L _____ (2)
Comparing eq 1 & 2
VB = - ΔV/L
VB = -Є/L
Є = - VBL
If Ѳ is the angle between V and B
Є = -VBL SinѲ
(www.pak-physicsnotes.blogspot.com)
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