Inducing electricity w/ moving piece of metal, static magnet

[kallesmajs]

Hi!

I'm curious to know, whether it is possible to produce electricity by moving a piece of metal over a magnet (i.e a immobile magnet and a moving piece of metal close to the magnet), and how this would be done in practice.

 

[Charles Link]

This is the principle behind an electric generator. The change in the magnetic field that the conductor (metal) experiences produces an internal EMF (electromotive force), basically a voltage, that generates a current that in addition, has electrical power. It is done basically universally, on a very large scale, and is also done on a much smaller scale, like the generator light for a bicycle where the tire turns the turbine to produce the electricity that lights the light.

 

[kallesmajs]

Thank you very much for your quick answer!

I assume, the same would not work, if for example we had a static(immobile) 'device' made up of a copper coil and a permanent magnet, whereas the moving conductor(metal) is not the one that we want to produce the electricity, but rather the copper coil?

 

[Charles Link]

Thank you very much for your quick answer!

I assume, the same would not work, if for example we had a static(immobile) 'device' made up of a copper coil and a permanent magnet, whereas the moving conductor(metal) is not the one that we want to produce the electricity, but rather the copper coil?

If the copper wire and magnet are both standing still, you don't generate any power.

 

[kallesmajs]

If the copper wire and magnet are both standing still, you don't generate any power.

Right, that is what i thought. But if we were to make the magnet follow the metal (imagine a closed box with a string from end to end in the box, and the string goes through a now mobile magnet. Around the string and magnet goes a coil, so that when we move the metal the magnet will follow the metal because its on a string and it will move inside a coil as well) it should generate right?

 

[Averagesupernova]

If the copper wire and magnet are both standing still, you don't generate any power.

This is wrong. Inductive pickup sensors work in this exact manner. While it is not generally the way we generate power it is a very practical sensor.

 

[Charles Link]

This is wrong. Inductive pickup sensors work in this exact manner. While it is not generally the way we generate power it is a very practical sensor.

$\\$ Editing: In more detail, I see where the OP's question could be interpreted this way. They have another conductor moving nearby. This generates currents and a weak changing magnetic field that can get picked up by a stationary coil. I did not interpret the OP's question in this manner though=from what I could tell the OP was interesting in generating electrical power-in a reasonably efficient manner. $\\$ In addition, if the moving material is ferromagnetic, e.g. iron, it could then get sufficient magnetization inside of it to produce a magnetic field of its own, but I believe this is beyond the scope of the OP's question.

 

[Charles Link]

Right, that is what i thought. But if we were to make the magnet follow the metal (imagine a closed box with a string from end to end in the box, and the string goes through a now mobile magnet. Around the string and magnet goes a coil, so that when we move the metal the magnet will follow the metal because its on a string and it will move inside a coil as well) it should generate right?

Presumably the metal in this case is e.g. iron, so that there is an attractive force between the iron and the magnet. When the magnet moves and changes position relative to a copper coil, yes, it should generate electricity. Suggestion is to google "Faraday's law" for additional information on how a changing magnetic field can generate electrical currents.

 

[Dadface]

Videos like this might be useful.

 

[Charles Link]

Videos like this might be useful.

@Dadface Very interesting. Thank you. Also of interest is copper actually is very much non-magnetic (I believe only slightly diamagnetic) in its response to a static magnetic field. A change in the magnetic field can however induce large currents to create sizable magnetic fields that act to repel the magnet and keep it from falling quickly. I was still very surprised to see the effect is as strong as it is. Very interesting.

 

[Windadct]

There is a process for learning these concepts! Typically it involves the old magnet and iron filings. This helps show the shape of the magnetic field, and illustrates magnetic flux lines ( noting that lines of flux is really more of an analogy than reality)... anyway, we can now visualize the magnetic field. We "play with other magnets, magnetic items, and see how the field reacts.

Next we often see the compass type experiment, where we pulse current through a wire near a compass and see the compass needle deflect, demonstrating that current in the wire creates a magnetic field ( Amperes law) AND that the magnetic field can apply a force on the compass needle. By arranging the compass and wire differently we can change the type of deflection (reaction - magnitude and direction) of the needle. Additionally it needs to be noted that the same force ( well equal an opposite) is applied the the wire - according to Newton's 3rd.

As our physics education continues - we perhaps have a small coil and magnet, with the coil connected to a galvanometer ( very sensitive current meter) - we see that we can create a current by passing the magnet through, or by the coils.

We may build a small dc motor / generator, with with we see, and demonstrate a machine, utilizing these concepts to turn electrical current into mechanical motion ( motor) or mechanical motion into electrical current (generator) - etc.

In the end we see or know that a conductor in a varying magnetic field will have a current induced in it, and visa-versa. The filed can vary in essentially any manner, the magnet and conductor moving relative to one another, the mag field could be created by another electrical circuit (conductor or coil) and be expanding or collapsing as the current is changing in that conductor, or the magnetic field could be affected by the "movement" of a magnetic material, or even another conductor in the area. But the core concept is that the relationship of the field and the conductor must be changing.