Page 88 - Basic Electrical Engineering

or,

where L is in Henry, e is in Volt, and is in Ampere per second.

When steady direct current flows through an inductor, it will not affect the
circuit as there is no change in current. Inductors are of two types viz air-core

type and iron-core type. Inductors are also called chokes. Inductors are
available in all current ranges. Air-core inductors are wound on bakelite or

cardboard rods and are extensively used in electronic circuits in millihenry
and microhenry ranges. High-value inductors are made of iron core. They are

mainly used in ac power supply of frequency of 50 Hz.
The details of self and mutual inductance have been discussed earlier.

1.19.3 Capacitors

A capacitor, in its simplest form, consists of two thin parallel plates of
conducting material separated by a dielectric material. A capacitor is capable
of storing charge when a voltage is applied across the capacitor plates. If a

voltage source, say a battery, is connected across the two plates of a parallel
plate capacitor as shown in Fig. 1.19, electrons from the negative terminal of

the voltage source accumulate on plate A of the capacitor. The other plate B
loses electrons as it is connected to the positive terminal of the source of

voltage. This way, the excess electrons produce negative charge on one side
of the capacitor while the opposite side will have positive charge. The

dielectric material placed in between the plates hold the charge because the
free electrons cannot flow through an insulator (i.e., the dielectric material
like air, paper, or mica). Storage of charge by a capacitor means that the

charge remains in place even after the voltage source is disconnected.
Capacitance of a capacitor is the ability to store charge. Charging and

discharging are the two main effects of capacitors. When a voltage is applied,