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What Happens to an Inductor’s Stored Energy When Current Stops?

Can the Energy Stored in an Inductor Be Used Practically? Applications, Benefits, and Real-World Examples. Why does an inductive load create sparking across contacts? 

An inductor stores energy in the form of a magnetic field as long as current is flowing through it. As the current stops, the magnetic field began to collapse. Collapsing magnetic flux is also a rate of change of magnetic flux that will induce a large voltage spike (back EMF) across it.

Energy stored in an Inductor: 

Magnetic energy stored in a Inductor

Since this induced voltage is parallel to the inductor coil, it decays by converting it to heat across the coil resistance. In that process, the coil generates a magnetic field again due to the flow of decaying current through the coils, which results in electromagnetic interference in the radio operation and sparking across open contacts.

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Adverse effects of stored energy in an inductor: 

Sparking across contact due to inductive load

Can we put this back-EMF into use? Yes.

Practical Use of Stored Energy in an Inductor: 

Spark-ignition in petrol fuel automobiles:

Spark Ignition  circuit in a petrol car

When the contact breaker closes, current flows in the coil to store magnetic energy. When the breaker point opens, the magnetic field collapses to generate a high voltage pulse across the spark plug to generate a spark.

Tube light Ballast (choke):

Electrical circuit of florescent Tube Light


When the starter bimetallic plate contacts close/open, a high voltage is generated across the fluorescent tube to initiate the mercury vapour ionisation process, which creates light.

FAQ Set

Q1: Can the energy stored in an inductor be used practically?
Yes, the energy stored in an inductor’s magnetic field can be harnessed in applications such as boost converters, energy recovery circuits, and switching power supplies.

Q2: How is energy extracted from an inductor?
When the current through an inductor decreases, the collapsing magnetic field induces a voltage that can be used to power a load or charge a capacitor, following Faraday’s law of electromagnetic induction.

Q3: What are common applications of inductors using stored energy?

  • DC-DC converters (buck/boost)

  • Flyback transformers

  • Energy recovery in electric vehicles

  • Smoothing in power supplies

Q4: Why does an inductive load cause sparking across switch contacts?
Inductive loads resist sudden changes in current. When a switch opens, the inductor tries to maintain the current flow, generating a high-voltage spike across the contacts, which causes arcing or sparking.

Q5: How can sparking be reduced in inductive circuits?
Using snubber circuits, flyback diodes, RC networks, or varistors across the load or switch can safely dissipate the energy and minimise contact arcing.

Q6: Are all inductive loads prone to contact sparking?
Yes, any load with significant inductance, such as motors, relays, solenoids, and transformers, can produce sparks if switched abruptly without protective measures.


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