Figure 20. Growth And Decay of Current In An LR Series Circuit.

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Electrical inductance is like mechanical inertia, and the growth

of current in an inductive circuit can be likened to the

acceleration of a boat on the surface of water. The boat does

not move at the instant a constant force is applied to it. At

this instant, all the applied force is used to overcome the

inertia of the boat. Once the inertia is overcome, the boat

will start to move. After a while, the speed of the boat

reaches its maximum value, and the applied force is only used in

overcoming the friction of the water against the hull.

When the battery switch (S1) in the LR circuit of figure 20, view

A, is closed, the rate of current increase is maximum in the

inductive circuit. At this instant, all the battery voltage is

used in