Friday, June 12, 2009

What Is Resistor Element?-All About Resistors

Resistor Definition

A resistor is a two-terminal electronic component that produces a voltage across its(resistors) terminals that is proportional to the electric current through it in accordance with Ohm's law: V = IR.

Resistors are elements of electrical networks and electronic circuits and are used in most electronic equipment. Practical resistors can be made of various compounds and films, as well as resistance wire (wire made of a high-resistivity alloy, such as nickel/chrome .

A resistor is coated with paint or enamel, or covered in molded plastic to protect it. Because resistors are often too small to be written on, a standardized color-coding system is used to identify them. The first three colors represent ohm value, and a fourth indicates the tolerance, or how close by percentage the resistor is to its ohm value. This is important for two reasons: the nature of resistor construction is imprecise, and if used above its maximum current, the value of the resistor can alter or the unit itself can burn up. 

Resistors can be integrated into hybrid and printed circuits, as well as integrated circuits. Size, and position of leads (or terminals) are relevant to equipment designers resistors must be physically large enough not to overheat when dissipating their power.

The primary characteristics of a resistor are the resistance, the tolerance and the power rating. Other characteristics include temperature coefficient, noise, and inductance. 

Every resistor falls into one of two categories Fixed or variable resistor
A fixed resistor has a predetermined amount of resistance to current, while a variable resistor can be adjusted to give different levels of resistance. Variable resistors are also called potentiometers and are commonly used as volume controls on audio devices.

A rheostat is a variable resistor made specifically for use with high currents. There are also metal-oxide varistors, which change their resistance in response to a rise in voltage; thermistors, which either raise or lower resistance when temperature rises or drops; and light-sensitive resistors. 

Resistor Electronic symbol

Resistors Unit

The ohm (symbol: Ω) is a SI-driven unit of electrical resistance, named after Georg Simon Ohm. Commonly used multiples and submultiples in electrical and electronic usage are the milliohm (1x10-3), kilohm (1x103), and megohm (1x106).

Some types of resistors

Carbon Resistor

Film Resistor

Wirewound Resistor

Ohm's Law Video

Ohm's Law Part 1: Units and Quantities

This video introduces the basic electrical quantities of charge, current, voltage, and resistance. The concept of quantities and units is explained. The units of Coulombs, Volts, Amperes, and Ohms are described. The three basic formulas of Ohm's Law (E=IR, I=E/R and R=E/I) are introduced. 

Ohm's Law Part 2: Ohm's Law Applied to

Simple Circuits

This video demonstrates the use of Ohm's Law to calculate current, voltage, and resistance in a simple circuit.