Charged inductor with no discharge path?

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SUMMARY

This discussion focuses on the behavior of an inductor in a DC circuit when the power supply is removed. When the current is interrupted, the collapsing magnetic field generates a back electromotive force (EMF), which can lead to a spark if a discharge path is not present. The inductor will initially produce a current pulse that charges its terminals, followed by a back current pulse that neutralizes the inductor. This phenomenon is commonly observed when unplugging devices, where the sudden interruption of current can create a noticeable spark.

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  • Understanding of basic DC circuit principles
  • Knowledge of inductors and their behavior in electrical circuits
  • Familiarity with electromotive force (EMF) concepts
  • Experience with electrical safety and handling of live circuits
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ShawnD
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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?
 
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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.
 

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