Some Basic Principles of Electronics

An example of its application is in the analysis of the water used in producing pharmaceutical formulations that must be free of organic contaminants. Such water can be monitored routinely in the company laboratory for the concentration of organic compounds using the TOC analyzer described here. 

Jessica Weinland, a laboratory technician for a pharmaceutical company, operates a TOC analyzer to monitor the organic contaminants in the water used in preparing pharmaceutical formulations. 

Resistance to electron flow is measured in ohm units and is symbolized by the letter R. The ohm unit is symbolized by the Greek letter omega (Q). A resistance slows the movement of electrons in a circuit much like a smaller-diameter pipe would slow the movement of water. While all electronic circuit components have a certain resistance, components known as resistors—components that have a certain defined resistance in ohms, kilohms (kO, or 103 Q), or megaohms (MQ, or 106 Q) and are inserted into circuits for their resistance values—are available. These usually are small, cylindrical epoxy or plastic packages with leads (short wires) protruding from each end and small granules of carbon or resistance wire inside to slow the electrons. Resistors are manufactured with different degrees of accuracy. One percent 

Current is a measure of electron flow rate in an electrical circuit, analogous to water flow rate through a pipe, and is symbolized by I. Current is measured in amperes (amps), symbolized as A miUiamperes (milliamps), symbolized as mA or microamperes (microamps), symbolized as ptA. An ampere is an electron flow of 6.23 xlO18 electrons per second passing through the circuit. 

Just as a narrower-diameter pipe reduces the water pressure in the pipe, a resistor reduces the voltage from the battery. We say that there is a voltage drop across a resistor. The amount by which a voltage is reduced can be calculated by Ohm s law. Ohm s law is the mathematical relationship between this voltage drop (V), the value of the resistance (R), and the current (I) through the resistor  

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