continuously circulate through the magnet and not leak off into

space.

When bar magnets are stored, the same principle must. he

remembered. Therefore, bar magnets should always be stored in

pairs with a north pole and a south pole placed together. This

provides a complete path for the magnetic flux without flux

leakage.

3. Inductance

The study of inductance presents a very challenging but

rewarding segment of electricity. It is challenging, in the

sense that new concepts are being introduced. The study of

inductance is rewarding in the sense that a thorough

understanding of it will. enable the student to acquire a

working knowledge of electrical circuits more rapidly.

a. *Characteristics of Inductance*. Inductance is the

characteristic of an electrical circuit that opposes the

starting, stopping, or changing of current . The above

statement is of such importance to the study of inductance that

it bears repeating. Inductance is the characteristic of an

electrical conductor that OPPOSES A CHANGE IN CURRENT. The

symbol for inductance is L, and the basic unit of inductance is

the HENRY (H). One Henry is equal to the inductance required to

induce one volt in an inductor by a change of current of one

ampere per second.

One does not have to look far to find a physical analogy of

inductance. Anyone who has ever had to push a heavy load

(wheelbarrow, car, etc.) is aware that it takes more work to

start the load moving than it does to keep it, moving. Once the

load is moving, it; is easier to keep the load moving than to

stop it again. This is because the load possesses the property

of INERTIA. Inertia is the characteristic of mass which opposes

a CHANGE in velocity. Inductance has the same effect on

current: in an electrical circuit as inertia has on the movement

of a mechanical object. It requires more energy to start or

stop the current than it does to keep it flowing.

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