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Lonley_Shepherd

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To find the emf generated by two ten turn coils, the planes of which are at 60 degrees in a radial magnetic field B=Bcos(theta)sin(omega*t) in the direction Ar, that rotates with omega rad/sec at the instant when the coil A1A2 makes an angle alpha with the plane of the maximum flux density.

Now to compute the emf we will ignore the effect of mutual inductance and will just calculate the field for each coil then add them.

we have: emf = -N (integral) dB/dt . ds + N (integral) v x B . dL

my problem is with the first term, the S area vector is in the direction of A(phi) as shown (talking about the A1A2 coil here) so the dot product result will be zero even though the differential of B is not zero.

now i checked it with my tutor then he says we have to consider another area as the flux is clearly not zero (not that clear to me), so:

ds= r*d(phi)*dz Ar to get a value for the flux in the loop.. !

what i can manage so far that he chose another area that enclosed the same path, but isn't the value of that term going to increase if we choose larger areas, so the more the area "chosen" the more the flux!.. then there's no exact magnitude for any area integral .. thanks for your help

Now to compute the emf we will ignore the effect of mutual inductance and will just calculate the field for each coil then add them.

we have: emf = -N (integral) dB/dt . ds + N (integral) v x B . dL

my problem is with the first term, the S area vector is in the direction of A(phi) as shown (talking about the A1A2 coil here) so the dot product result will be zero even though the differential of B is not zero.

now i checked it with my tutor then he says we have to consider another area as the flux is clearly not zero (not that clear to me), so:

ds= r*d(phi)*dz Ar to get a value for the flux in the loop.. !

what i can manage so far that he chose another area that enclosed the same path, but isn't the value of that term going to increase if we choose larger areas, so the more the area "chosen" the more the flux!.. then there's no exact magnitude for any area integral .. thanks for your help

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