TABLE OF CONTENTS This chapter will help to refresh and expand your understanding of basic electrical components and the basic terms used in electricity as required for instrumentation.
This chapter discusses
Basic passive components (resistors, capacitors, and inductors) used in electrical circuits
Applications of Ohm's law and Kirchoff's laws
Use of resistors as voltage dividers
Effective equivalent circuits for basic devices connected in series and parallel
The Wheatstone bridge
Loading of instruments on sensing circuits
Impedances of capacitors and inductors
It is assumed that the student has a basic knowledge of electricity and electronics and is familiar with basic definitions. To recap, the three basic passive components resistors, capacitors, and inductors as well as some basic formulas as applied to direct and alternating currents will be discussed in this section.
Electrical power can be in the form of either direct current (dc) (one direction only) or alternating current (ac) (the current reverses periodically, see Fig. 2.1). In ac circuits the electromotive force drives the current in one direction then reverses itself and drives the current in the reverse direction. The rate of direction change is expressed as a frequency f and is measured in hertz (Hz), i.e., cycles per second. Electrical signals travel at the speed of light. The distance traversed in one cycle is called a wavelength ?, the relationship between frequency and wavelength (meters) is given by the following equation:
| (2.1) |  |
where c is the speed of light (3 10 8 m/s).
