Inductor and Spring Analogy

Inductor and Spring Analogy

As its symbol shows that, inductor is like a spring, if you apply compression force on spring, it can’t change it position immediately, it’s due to inertia of spring. It’s inertia of body, which oppose the change of state; similarly if you apply electrical force on inductor, (here electrical force is voltage), current doesn’t start flowing instantaneously. It starts increasing exponentially. Inertia of inductor doesn’t allow the sudden change of current.

               

 

Initially, inductor behaves as open circuit, think about spring, at the moment, you apply compressive force on spring, it doesn’t start compressing suddenly. At that instant, the force applied to one end of spring, it can’t be felt at other end of spring. That is the condition similar to open circuit. After that, the force gradually increasing and can be felt from another end. Due to this property of spring, it is used as a shocker in bike, cars and other vehicles, so that, mechanical shocks can’t be felt directly to the rider. Similarly, in inductor, after applying voltage, current start increasing gradually.

If the Shocker or spring is completely compressed, at that instant, whatever force you apply, can be felt directly from other end. At steady state, inductor behaves as short circuit,

Whatever force we apply on spring, when it is compressed, it is stored as potential energy in spring. Now, it tends to restore its position. It gives the restoring force to the system to restore its position. (As per Newton’s Third Law, it’s reaction to the action)  Similarly, inductor starts storing the energy in the form of magnetic field. It is ½ Li^2.

If we apply sinusoidal AC voltage to the inductor, say, in first half cycle it is storing energy, in the other half cycle the polarity of voltage is reversed, this time, the inductor can’t change the direction of current instantaneously (current can’t change suddenly in inductor).  Inductor changes its polarity and supply the current back to the system. It starts discharging and giving energy back to the system. That is also a kind of reaction. The power associated with this reaction is nothing but known as the Reactive Power.