Presentation (4).pptx on motional emf electomagnetic induction

Motional EMF

1. Electromagnetic Induction

2. Motional Electromotive force Consider a conducting rod of length l moving with a uniform velocity v perpendicular to a uniform magnetic field B , directed into the plane of the paper. Let the rod be moving to the left as shown in figure. The conducting electrons also move to the right as they are trapped within the rod.

3. Conducting electrons experiences a magnetic force F = evB . So they move from P to Q within the rod. The end P of the rod becomes positively charged while end Q becomes negatively charged, hence an electric field is set up within the rod which opposes the further downward movement of electrons . Work done in moving charge q = F × QP = ( qvB ) × l e.m.f induced = work done per unit charge So , e = W/ q e = Blv Induced current = e / R I = Blv / R

4. Motional induced e.m.f in a conducting rod rotating in a uniform magnetic field Consider a magnetic field strength B directed into the paper perpendicular to its plane and PQ is a conducting road of length L rotating with uniform angular velocity in the plane of paper in a small time t let the road turn through small angle theta.

5. Numerical Problems