When i deenergized a coil, what polarity of its electrical potential?
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When we have an energized coil connected to a voltage source through a switch, current flows through the coil creating a magnetic field. But what happens when we suddenly open the switch and de-energize the coil?
Lenz's Law states that the induced voltage will always oppose the change in magnetic flux. When we de-energize a coil, the magnetic flux decreases. The induced voltage will therefore act to oppose this decrease by trying to maintain the original flux.
When the switch opens and current starts decreasing, the induced voltage must drive current in the same direction as before to oppose the flux change. This requires the induced voltage to have opposite polarity to the original applied voltage. The coil's left terminal becomes negative and right terminal becomes positive.
When the coil is de-energized, the back EMF can create a significant voltage spike that's much higher than the original applied voltage. This spike has opposite polarity and can damage sensitive electronic components. That's why protection circuits are essential in inductive loads.
In summary, when a coil is de-energized, the induced voltage polarity is opposite to the original applied voltage. This follows from Lenz's Law - the induced voltage opposes the change in magnetic flux. Understanding this principle is crucial for designing safe electrical circuits with inductive components.