Electromagnets and conservation of energy

[abccbaabc014]

Right, I'll try to get this question across.
Say you have 2 bar electromagnets, aligned so when you turn them on they are attracted to each other. You start with them touching, turn them on and pull them apart. You then turn of the current and put them back together. If you continue to repeat this, you are putting a lot of energy in, but where does it go? The only two answers I can think of are heat and EM radiation.

 

[Born2bwire]

Some of the energy also gets dumped back into the circuit when you turn off the electricity. Lenz's law will tell you that when you turn off the current that is supporting the magnetic field, then the field will try to keep a current to support itself. Some of the field's energy gets dumped back into the electromagnet in order to sustain itself and this gets dissipated as heat through ohmic losses. The changing magnetic fields and currents when you turn on and off the magnets will produce a small amount of electromagnetic radiation. The one you miss is the work done in separating the magnets. The magnets repulse each other over a distance producing work, this energy comes out of the magnetic fields (which is replenished by the currents in the electromagnet). The resulting kinetic energy is expended as heat due to friction.

So yes, in the end you eventually end up with waste heat and some EM radiation but the energy goes through various transfers until that point.

 

[astrokreng]

I can say that the conservation of energy principle applies to this situation. This principle states that energy cannot be created or destroyed, but it can be converted from one form to another. In the case of the electromagnets, the energy is being converted from electrical energy to magnetic energy when the current is turned on. When the magnets are pulled apart, some of this magnetic energy is converted to kinetic energy, causing the magnets to move. When the current is turned off and the magnets are put back together, the kinetic energy is converted back to magnetic energy. This process can continue indefinitely as long as the electrical energy is supplied to the magnets.

Additionally, as you mentioned, some of the energy may be lost as heat due to friction between the magnets and the surrounding air. However, this does not violate the conservation of energy principle as the energy is simply being converted to a different form.

In regards to EM radiation, it is possible that a small amount of energy may be released in the form of electromagnetic waves. However, this amount would be negligible compared to the energy being put into the magnets and would not significantly impact the conservation of energy.

In summary, the energy put into the electromagnets is conserved and can be seen in the form of magnetic and kinetic energy. Any energy lost as heat or EM radiation is minimal and does not violate the principle of conservation of energy.