**Resistor Terms:**

'A', 'B', 'C', 'D/E', 'F-L', 'M', 'N', 'O', 'P', 'R', 'S', 'T', 'V-Z'

**Ohm.** The unit of electrical resistance. That value of electrical resistance through which a constant
potential difference of 1 volt across the resistance will maintain a current flow of 1 ampere through the
resistance.

**Ohmic Value.** Resistance in ohms.

**Ohmmeter.** A meter used to measure resistance. In almost all cases an ohm meter is just one of a number of functions found in a multi-meter. Modern Ohm Meters are completely digital [lower right] and have a very high input resistance, while older ohm meters were completely analog in nature [below]. In addition to measuring ohms a multimeter will also measure current, DC volts and AC volts. Refer to the Test Equipment Manufacturers page for vendors.

**HP Digital Multi-Meter**

**Ohm's Law.** The current in an electrical circuit is directly proportional to the electromotive force in the circuit. The most common form of the law is E = IR, where E is the electromotive force or voltage
across the circuit, I is the current flowing in the circuit, and R is the resistance of the circuit.

**Ohms per Square.** The resistance of any square area of thin film resistive material as measured
between two parallel sides.

**Open Element.** A component or adjustable resistor which has its resistive element exposed. An open-element resistor supported by a frame but not totally surrounded by an enclosure. The graphic to the right shows an example of a low cost board mount [vertical mounting] adjustable resistor. An open-element potentiometer might be of lower cost compared to other alternatives but is more susceptible to contamination due to dirt or other objects.