Resistors

Define the 3 purposes for using resisters in a circuit.

1: To Generate Heat 2: To limit current 3: To divide voltage

Temp Coefficient

The amount of resistance change due to temperature change. The lower the temperature coefficient the less it is affected by environment temperature

Resistance

The components opposition to current flow.

Power Rating

The maximum amount of power it is designed to dissipate. Identified by size

Carbon Composition Resistor

A compound of carbon graphite and a resin bonding material. Cheap to make but change their value with age or heat.

Tolerance

A plus or minus percentage that the resistance value of the resistor is allowed to vary. The lower the tolerance the more precise.

Variable resistor

A resistor whose values can be changed or varied over a range.

Potentiometer

A variable resistor used as a voltage divider with three terminals

carbon film resistor

Coating a ceramic rod with a film of carbon instead of metal. Less expensive that metal film resistors and have a high tolerance than carbon resistors.

metal glaze resistor

Fixed resistor made by combining metal with glass. Compound is applied to a ceramic base as a thick film.

definition of a fixed resistor

Fixed resistors have one ohmic value and cannot be changed or adjusted.

Wire-wound resistors

Made by winding a piece of resistive wire around a ceramic core. Used when a high power rating is needed.

Reliability

The percent of failure after 1000 hours of operation at its maximum power rating. The lower the percentage the more reliable the resistor is.

Rheostat

a variable resistor with two terminals. Used to adjust current value

Metal film resistors

Resistors constructed by applying a film of metal to a ceramic rod in a vacuum. Do not change in value with age.