Charged inductor with no discharge path?

AI Thread Summary
In a DC circuit with an inductor, removing the power supply while the magnetic field is established leads to a collapse of the field, generating a back EMF. If there is no discharge path, the current and voltage generated by the collapsing field can create a spark, which dissipates the energy. Without a spark, the back EMF initially causes a current pulse that charges the inductor's ends, followed by a back current pulse that neutralizes it. The resistance of the inductor limits the voltage during this process. This phenomenon is often observed when unplugging devices, highlighting the importance of managing inductive loads.
ShawnD
Science Advisor
Messages
715
Reaction score
2
Suppose I have a simple DC circuit. If I wrap the wire around a piece of iron, I create an inductor. Having a steady flow of current creates a steady magnetic field around the piece of iron. If I remove the power supply and put a wire in its place, the magnetic field will collapse and send a current back in the opposite direction of the current which created the field.

What happens if I don't have a nice discharge path? What if I charged the inductor then cut the wire? The field still collapses, but where does my current/voltage go?
 
Physics news on Phys.org
For DC current, the inductor will have a current, but only a small voltage, due to its resistance, across it. When you cut the wires, a large back EMF will be applied as the magnetic field collapses. This could institute a spark whose current will end the voltage due to the EMF. This is what you notice sometimes when you remove a plug.
If there is no spark, the EMF will first cause a current pulse in the inductor that will charge the ends, followed by a back current pulse that neutralizes the inductor.
 
Thread 'Motional EMF in Faraday disc, co-rotating magnet axial mean flux'
So here is the motional EMF formula. Now I understand the standard Faraday paradox that an axis symmetric field source (like a speaker motor ring magnet) has a magnetic field that is frame invariant under rotation around axis of symmetry. The field is static whether you rotate the magnet or not. So far so good. What puzzles me is this , there is a term average magnetic flux or "azimuthal mean" , this term describes the average magnetic field through the area swept by the rotating Faraday...
Back
Top