Electrical circuits

We begin this chapter with a brief review of the properties of electrical circuits.

Conductive materials, such as copper, exhibit the ability to easily produce an electric current in the presence of an electric field. Nonconductive materials, for example, glass, rubber, and polyvinyl chloride (PVC), inhibit the flow of electricity so thoroughly that they are used as insulators to protect electrical conductors against short circuits. In metals, electrical current consists of electrons in motion. Materials that permit some electrical current to flow, while predictably restricting the amount allowed to flow, are used in the construction of resistors.

The relationship between electrical current, voltage, and resistance in a circuit is analogous to the relationship between flow rate, pressure, and flow restriction in a hydraulic system. Consider a kitchen water tap: pressure in the pipe leading to the tap forces water to flow when the valve is opened. If the...