I’ve read somewhere that magnets dont do work so they dont use energy, but then how come they can move metallic objects? where is that coming from?
In: Physics
Potential energy, similar to gravity. If you lift a ball from the floor, you do work to separate the ball from the lower energy state (e.g. being closer to Earth’s gravitational center). When you drop it, that energy is converted to kinetic energy.
Same goes from magnets.
If a permanent magnet attracts some object, then one of the two happened before:
* The object was first moved away from the magnet, which required energy
* Something got magnetized which wasn’t a magnet before, which also required energy
In both cases, there is no way to create energy out of nothing.
This simple question would destroy 100% of the “free energy” or “perpetual motion machine” videos lying around.
Magnets can convert energy from one form to another, but not create it.
You can store energy too, and it is this stored energy that is converted to kinetic energy when magnets attract each other. To get the magnets back apart you have to put that energy back in.
If you hold a magnet and push another magnet away with it, the energy is coming from your hand.
They don’t use energy because, from the perspective of the magnets, opposing poles closer together is a lower energy state than further away; the universe is constantly moving things from higher energy states to lower energy states.
Unfortunately, this is one of those “just the way things are” kind of things that doesn’t have a particularly deep or meaningful answer. It’s just easier for opposing charges to exist closer than further. Someone mentioned gravity and that’s the best example. We don’t usually think of objects and the Earth as a system pulling on each other, but that’s the case. The same way it takes effort to lift something but it’ll fall without any effort, opposing charges require effort to separate and will fall together if unopposed.
Strictly speaking that’s true. The magnets themselves do not exert any energy. The energy that brings them together is actually coming from the magnetic field generated.
Magnets do not consume energy to function, but they do perform ‘work’ on nearby metal. When a magnet attracts something (another magnet or a piece of metal) the work done is force x distance. (Since force varies with distance, you’ll actually have to do an integral).
Work = energy. Energy is conserved because this energy is converted into heat and sound at the moment of impact. If either piece is covered in rubber or plastic, that material will deform and most of the energy is converted to heat. If it’s metal hitting metal, most of the energy will turn into the sound waves of a CLACK!
This amount of energy is also the same amount of energy (Ignoring friction) that you would need in order to pull the magnets apart again.
As to how the magnet pulls on things without consuming energy to function in the first place: it’s just a fundamental force of the universe, as others have said. You can’t break it down more than that.
Magnetism is one of the 4 fundamental forces of nature, like gravity. In a sense, these represent a limit of our scientific understanding – we don’t really know *why* magnetic fields come and go with electric fields (like gravitational fields with mass), we simply observe that they *do*, and quantify the strength of the force we observe.
Sorry for the obtuse sounding answer, but I think you might be asking a more fundamental question about forces.
so the magnets always wanted to
be together. We’ve managed, somehow, to find a method that increases their want,
their need, to be back together,
TLDR: [In classical physics](https://www.youtube.com/watch?v=fHG7qVNvR7w), there isn’t really a way to explain how magnets do work (i.e. exert a force to move stuff.) It takes quantum physics, specifically spin, to describe how magnets exert force.
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