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I'm trying to under stand electromagnetic induction more and have been looking up all the ways to induce a coil with a magnet and keep only finding these three types of examples.

enter image description here

I’m confused as to why these are the only three I can find and can’t find an example like the image below. enter image description here

The brown arrow is the direction of magnetic force and green arrow is the direction of the movement for the magnet. Can some one help clear this up for me cause every were I look on Google and Youtube I can’t find this as a way to induce electricity and its been bothering me.

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You don't see the set-up in your lower diagram given as an example of how to induce an emf? This is because it is is not a particularly good way to induce an emf; the emf will only be small.

Imagine the magnetic field lines coming out of the North Pole of the magnet and curling round to re-enter the magnet at its South Pole. The turns of the coil to the left of the magnet will be threaded through by field lines with a right-to-left trend; those to the right of the magnet will be threaded through by field lines with a left-to-right trend. When the magnet is moved as shown, there will be an increasing number of turns to the left of the magnet and a decreasing number to the right, so the right-to-left flux linkage will increase and the left-to-right flux linkage will decrease. These effects will re-inforce to produce a resultant emf. The emf won't be very large because most of the magnetic field lines pass more or less diametrically through the coil and therefore thread through hardly any turns, and this doesn't change as the magnet is moved.

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  • $\begingroup$ Hey so I did an experiment to test it to see how much Energy it would generate and it generated the same amount from the magnets going outside along the side of the coil compared to going inside the coils from the center. $\endgroup$ – Chris Herdeg Dec 30 '19 at 0:18
  • $\begingroup$ Well done! Was it the voltage that you were measuring? How did you ensure that you were moving the magnet at the same speed each time? Were you using a long coil as in your diagram? $\endgroup$ – Philip Wood Dec 30 '19 at 9:05
  • $\begingroup$ Yes, I got 20mV on both test same coil and magnet. So why isn't it that if they generate the same voltage I can't find this way of generating a voltage on the internet anywhere. Please send me the website or youtube video of this demonstration cause I cannot find any. $\endgroup$ – Chris Herdeg Dec 31 '19 at 20:44
  • $\begingroup$ Can't help, I'm afraid; I've never seen it demonstrated. Why don't put your own your own experiment on Youtube? $\endgroup$ – Philip Wood Dec 31 '19 at 21:10
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To describe electromagnetic induction, we use a mathematical object, fundamental in magnetism, called the magnetic field . You can think of it as arrows in space which, following a couple of equations, tell you how they would change the motion of magnets or charges. Here is a figure you have probably seen before showing the magnetic field created by a bar magnet: enter image description here

Electromagnetic induction refers to what happens when this field changes over time, described with a physical law, named Faraday's Law. This Law says that when a magnetic field through, for example, a wire changes in any way, then another physical object, named the electric field, arises. This electric field causes charges in a wire to move, which creates a current.

(If you are interested in the mathematics of the phenomenon, or a more detailed source, see Faraday's Law)

In the three cases you show above, the magnetic field through the coil changes (either because the coil and the magnet get closer, or because the direction in which the magnet faces the coil changes).

In the image you show below, the magnetic field on the left and right of the magnet changes, but (and here is the most important part) due to the symmetry of the system, the augmentation in one side has an equal decrease on the other, hence, the overall change is zero.

IMPORTANT NOTE: When I said the overall change of the magnetic field on the coil is zero, I assumed the coil was much bigger than the magnet so we can neglect edge effects. The real physical change is that the difference in the change on both sides is small, which induces a really small emf, which generates a current with small magnitude.

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