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Electric and magnetic fields are different from each other(i think i am correct).. How does changing magnetic field induce electric current??? enter image description here

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  • $\begingroup$ Electric fields and magnetic fields are just different components of the electromagnetic field. The (classical) relationship between the field's components is described by Maxwell's equations. $\endgroup$ – Alfred Centauri Oct 16 '13 at 11:38
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Alfred and Sam29 are quite correct, but the Maxwell equations and saying electric and magnetic fields are just different components of one thing, the electromagnetic field, is just a (nicely consistent) way of representing what is observed in nature.

It does not answer the question of why it is observed in nature.

I'm not sure there is a good answer (other than "it just is"), but I would propose a poor answer:

I assume you have no problem with the principle of the electromagnet. If you run a current through a wire, a magnetic field is observed around the wire. This can be exploited to make powerful magnets. Turning on the current causes the field to appear, and turning it off makes it disappear. Turning the current on half-way gives you half of the magnetic field.

Then, all you have to do is see there's no reason to suppose the relationship is one-way only. Then if you supply the magnetic field from outside, if it's two-way, you should see a current, and you do.

There's a simple demonstration:

Take a flashlight battery, and take a short piece of wire connected to one end of the battery, and tap it on the other end. You see a tiny spark.

Now do the same thing with a long piece of wire in a coil (making an electromagnet). You get a fat spark.

Why? Because when you disconnect the wire from the battery, the magnetic field in the electromagnet doesn't just disappear, its change induces current in the coil.

Again, it may be easier to see that, because of conservation of energy and whatnot, the relationship between current and magnetic field has to be two-way.

Then, Maxwell's equations make a beautifully concise explanation of that two-way relationship.

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Electric fields and magnetic fields are very related. This can be summarized as: a changing magnetic field creates a changing electric field (and vice versa). Moving the magnet closer changes the magnetic field at the coil, creating an electric field in the wire.

Have you learnt about the force of a magnetic field on a charge yet? If you have, then here's another way to think of it. Imagine instead of moving the magnet into the coil, you moved the coil to the magnet. By the Lorentz force, the charges in the wire would move in a spiral e.g along the wire.

Moving the wire through the magnetic field is physically the same as increasing the magnetic field at the coil. That's why changing the magnetic field creates a current.

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    $\begingroup$ Why it is like that ? I mean why a charged conductor produce magnetic field or why when we cut magnetic flux, it induces current ? what is the reason ? $\endgroup$ – Happy Coder Feb 17 '14 at 12:56
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As Alfred correctly pointed out, both the electric and magnetic fields are fundamentally the same field, the electromagnetic field - they are just different components. By this logic, naturally, if you were to somehow change one component (by moving a magnet or something of that sort), it would lead to a change in the other. Keep in mind that this obviousness is now easier to see because of Maxwell's laws. Before them, many physicists tried to answer the same question using their own approaches, and they failed. Electromagnetic theory gives answers in perfect harmony with experiments. I suggest you look up the laws, and that would answer your question better than any of us here could.

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