4/15/2023 0 Comments Flux meaning![]() I hope this clears up the difference.NEW! A digital journal for innovative original research and fresh, bold ideas in clinical trial design and clinical decision-making. This is what the $cos\theta$ term is telling us - and why the integral expression is really the right way to look at this (but that may be a bit more advanced than you need right now). It's not that the area of the coil changes, but the "area that sees the magnetic field" changes. Put differently, this is how you can see that flux changes when a coil rotates in a magnetic field. You were right on the first three case 4 is flux cutting (the geometry changes).Īs for your "unrelated question": in the expression $$Flux=B A$$ $A$ is the area of the solenoid normal to the B field - so if you have a homogeneous B field at an angle $\theta$ to a plane coil, $$Flux = B A cos\theta$$ because that is how you would count "the number of flux lines going through the area of the coil". You gave four cases to test your understanding. The following excerpt from an online A-level physics course shows this in a diagram: ![]() In that case, the geometry didn't change, and we speak of flux linking. On the other hand, if my loop is already inside the C magnet and I rotate it, once again I change the dot product of area and B (this time by changing the angle).įinally, if I hold the loop still and change the field of the magnet, I change the flux because the value of $B$ changes. For example, if I move a loop into the opening of a C shaped magnet, I "cut" through lines of B and see a sudden flux in my loop. When we talk of flux cutting, we usually mean "the dot product of the area and the B field is changed because their geometric relationship changed". You can see from this expression that you can change the flux either by changing the area, or by changing the value of B, or the angle between them. The flux encompassed by a coil is the integral of B over area: ![]() Is $A$ the cross sectional area of the solenoid?) Flux cutting.Īn AC-generator coil spins in a magnetic field, changing the magnetic flux through the coil. This is flux linking.Ī metal conductor moves through the magntic field of a magnet and cuts its field lines. When the flux of the primary coil in a transformer changes, the flux linked with the secondary coil changes. When a magnet falls through a long metal tube, the field lines of the magnet cut the tube. On reading the answers given I think I understand, but just to make sure, would these staments be correct: If this is however the case what do we call it when the magnetic flux density is changing and there is no relative motion? (a definition of both would be helpful) This makes no sense to me as depending on the reference frame either could be happening so they seem to be indicating the same thing. I was originally under the impression that flux cutting was when there was relative motion between a conductor and a magnet and linking was when there was a change in the magnetic flux density.Īfter reading, it seems that flux linking is when a magnet is moving and a conductor is still whilst flux cutting is the other away round. I am a bit confused about the difference between flux cutting and flux linking when talking about magnetic fields and induced EMF.
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