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nonequilibrium
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The non-conservative nature of an induced E-field due to a changing magnetic flux has always interested me.
In the case of a constant magnetic field and a circuit with a changing surface, the changing magnetic flux can actually be written as a line integral of v x B (*), with v the speed of the changing circuit at each point. So basically you're integrating the Lorentz Force qv x B around a closed circuit (or generally: loop). This means the non-conservative nature of this law (or anyway as far as motional emf is concerned) arises out of the concept of Lorentz Force. Why is this, as B is actually defined by the Lorentz Force?
Maybe you don't understand what my problem is. It is the fact I don't understand why it directly arises out of the Lorentz Force. For example: a free charge undergoing the Lorentz Force is experiencing a conservative force (since no work is ever done), but in the case of a charge in a conductor, you don't even need anything more than the Lorentz Force to make it non-conservative. Maybe it has something to do with the Hall-effect, but I honestly have no clue.
Thanking all helpers,
mr. vodka
(*) int([v x B] .dl) = - int(B. [v x dl]) = - d(phi)/dt (cf. Electromagnetic Fields and Waves, Lorrain, Corson, Lorrain [p413])
NB: In class when we have to calculate the current in a circuit with an induced E-field, we pretend there is an imaginary voltage source with the same emf as associated with the changing magnetic field and then we ignore the magnetic field. Is it obvious this should work? I do not understand why this little trick is allowed (for one thing: you're making a non-conservative electric field a conservative one)
In the case of a constant magnetic field and a circuit with a changing surface, the changing magnetic flux can actually be written as a line integral of v x B (*), with v the speed of the changing circuit at each point. So basically you're integrating the Lorentz Force qv x B around a closed circuit (or generally: loop). This means the non-conservative nature of this law (or anyway as far as motional emf is concerned) arises out of the concept of Lorentz Force. Why is this, as B is actually defined by the Lorentz Force?
Maybe you don't understand what my problem is. It is the fact I don't understand why it directly arises out of the Lorentz Force. For example: a free charge undergoing the Lorentz Force is experiencing a conservative force (since no work is ever done), but in the case of a charge in a conductor, you don't even need anything more than the Lorentz Force to make it non-conservative. Maybe it has something to do with the Hall-effect, but I honestly have no clue.
Thanking all helpers,
mr. vodka
(*) int([v x B] .dl) = - int(B. [v x dl]) = - d(phi)/dt (cf. Electromagnetic Fields and Waves, Lorrain, Corson, Lorrain [p413])
NB: In class when we have to calculate the current in a circuit with an induced E-field, we pretend there is an imaginary voltage source with the same emf as associated with the changing magnetic field and then we ignore the magnetic field. Is it obvious this should work? I do not understand why this little trick is allowed (for one thing: you're making a non-conservative electric field a conservative one)
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