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| Motional e.m.f and Faraday's Law |
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| Suppose a uniform magnetic field B perpendicular to the plane of paper point outward is represented in the region ABCD. A rectangular loop PQRS is pulled such that it moves with a velocity V as shown in the diagram. |
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| Motional emf and Faradays |
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This way the area of the loop inside the field changes. This induces an e.m.f in the wire. If in a small time  , the loop moves a distance  , then the decrease in the area of the loop = - lDx. |
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 where |
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| If R is the resistance of the loop, |
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| The direction of the current is given by Fleming's right hand rule. The induced e.m.f. Blv is called motional e.m.f. |
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| The motional e.m.f can be understood by recalling Lorentz force. When the loop moves, the charges inside it moves and so experiences a force = q v b [as the loop is placed in a external magnetic field]. The work done in moving the charge is q v b.l. |
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But e.m.f  |
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| Motional e.m.f = B l v |
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| Similarly when a conductor is stationary, the moving magnet or changing magnetic field produces an electric field which forces the charges in the conductors to move thus inducing current in the conductor. |
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