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Magnetic flux 
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#19
Jan214, 05:06 PM

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Thanks
PF Gold
P: 4,759

Then you use the Blv law.
The Blv law applies even in situations where there is moving media and Maxwell's equation del x E =  dB/dt does not apply. In your case the area is formed by the motion of the wire: delta area = lv per second, so dA/dt = B dA/dt = Blv. 


#20
Jan214, 05:08 PM

P: 399

I can't understand how changing area changes flux since the geometrical shape of wire is constant so the flux should be constant!! 


#22
Jan214, 05:11 PM

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PF Gold
P: 4,759

Area changes as vl. Think of the wire sweeping the area behind it as it moves in the perpendicular B field. dA/dt = lv. 


#23
Jan214, 05:27 PM

P: 75




#24
Jan214, 05:31 PM

P: 853

for a physical picture imagine a simple dc electric motor, you have stationary magnets and a rotor which has wires through it that form coils, these wires are constantly moving and " cutting" through the field of those magnets and current is being produced.



#25
Jan214, 06:06 PM

P: 75

Fortunately, this gives a result equivalent to the flux rule for motional emf. 


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