Inductors and Inductance
We found in Chapter 26 that a capacitor can be used to produce a desired electric field. We considered the parallel-plate arrangement as a basic type of capacitor. Similarly, an inductor (symbol J.2QQ,) can be used to produce a desired magnetic field. We shall consider a long solenoid (more specifically, a short length near the middle of a long solenoid) as our basic type of inductor. If we establish a current i in the windings (or turns) of an inductor (a solenoid),the current produces a magnetic flux 4>8 through the central region of the inductor. The inductance of the inductor is then
in which N is the number of turns. The windings of the inductor are said to be linked by the shared flux. and the product Ncf>8 is called the magnetic flux linkage. The inductance L is thus a measure of the flux linkage produced by the inductor per unit of current.Because the SI unit of magnetic flux is the tesla-square meter, the SI unit of
inductance is the tesla-square meter per ampere (T . m2/A). We call this the henry (H), after American physicist Joseph Henry, the co discoverer of the law of induction and a contemporary of Faraday. Thus. Through the rest of this chapter we assume that all inductors. no mailer what then geometric arrangement. have no magnetic materials such as iron in their vicinity Such materials would distort the magnetic field of an inductor.