How can magnetism generate electricity?

Answer 1

E=cB =zH = zcD: Electricity is related to magnetism by c and z (free space impedance).
Electricity and magnetism are essentially the same force. Electricity is produced by passing a wire through a magnetic field, or by rotating the wire, or by rotating a magnet around a wire. Motion of the magnet/wire induces an electrical current with the wire.

Answer 2

The first law of thermodynamics is that matter/energy cannot be "created" or destroyed. We can convert energy from one form to another. For instance, in a car, we convert chemical energy (actually the binding energy of electrons) to heat, which in turn is converted to kinetic energy (motion).

Your question has a similar answer. When you rotate a magnet, you are using kinetic energy to move it. This kinetic energy can be converted to electrical energy by taking advantage of the properties of electromagnetism. Since you can't "create" energy, the amount of electrical energy produced will always be the same or less than the amount of energy you put in. Actually, it can't be exactly the same, because there is always at least some energy converted to heat by friction. This wasted energy results in an energy conversion "efficiency" which is less than 100%. The classic application of your example is the electric generator.

One of the most useful and beautifully symmetric principles in physics is the connection between electricity and magnetism. This connection can be described like this. Electronsfeel the force exerted by a magnetic field. This is because electrons behave like tiny magnets, with North and South poles. So a magnetic field will have an effect on electrons in that field. If the field moves, the electrons in it will try to move. Conversely, if we have electrons in motion (electric current in a wire, for instance), these moving charges exert a magnetic force (because of their magnet-like property). So, if you glue a magnet onto an axle, and turn the axle, you create a spinning magnetic field. Place a length of wire around the spinning magnet, and an electric current (moving electrons) will occur in the wire. This is called induction. If you wrap the wire multiple times around, you increase the amount of current induced. You can verify this if you have a very sensitive ammeter to measure the current with. Now we can also take a length of wire and coil it up, then run electric current through it. Because of the magnetic properties of electrons, this coil becomes an electromagnet. And we could go even further. Take that electromagnet, and spin it (we'll use something called 'slip rings' to keep our wires from twisting up), and you have another spinning magnetic field from which you can induce electricity.

Answer 3

Faraday's law of electromagnetic induction effectively means that a moving magnetic field generates an electric field and therefore an electric current. Interesting experiment: move a magnet through a coil of wire connected to an LED.