A resistor is a passive two-terminal electrical component
that implements electrical resistance as a circuit element. The current through a resistor is in direct proportion to
the voltage across the resistor's terminals. This relationship is represented
by Ohm's law: V= I x R
where I is the current through the conductor in units of
amperes, V is the potential difference measured across the conductor in units
of volts, and R is the resistance of the conductor in units of ohms. The ratio of the voltage applied across a resistor's
terminals to the intensity of current in the circuit is called its resistance,
and this can be assumed to be a constant (independent of the voltage) for
ordinary resistors working within their ratings.
Resistors are common elements of electrical networks and
electronic circuits and are ubiquitous in 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). Resistors
are also implemented within integrated circuits, particularly analog devices,
and can also be integrated into hybrid and printed circuits.
The electrical functionality of a resistor is specified by
its resistance: common commercial resistors are manufactured over a range of
more than nine orders of magnitude. When specifying that resistance in an
electronic design, the required precision of the resistance may require
attention to the manufacturing tolerance of the chosen resistor, according to
its specific application. The temperature coefficient of the resistance may
also be of concern in some precision applications. Practical resistors are also
specified as having a maximum power rating which must exceed the anticipated
power dissipation of that resistor in a particular circuit: this is mainly of
concern in power electronics applications. Resistors with higher power ratings
are physically larger and may require heat sinks. In a high-voltage circuit,
attention must sometimes be paid to the rated maximum working voltage of the
resistor.
Practical resistors have a series inductance and a small
parallel capacitance; these specifications can be important in high-frequency
applications. In a low-noise amplifier or pre-amp, the noise characteristics of
a resistor may be an issue. The unwanted inductance, excess noise, and temperature
coefficient are mainly dependent on the technology used in manufacturing the
resistor. They are not normally specified individually for a particular family
of resistors manufactured using a particular technology. A family of
discrete resistors is also characterized according to its form factor, that is,
the size of the device and the position of its leads (or terminals) which is
relevant in the practical manufacturing of circuits using them. - (text by Wikipedia.org)
Here's a great flash game about resistors called 'When Resistors Gone Bad', a version of a popular NES game 'Space Invaders' with the objective of hitting a group of 'alien resistors' in different colors (colors of which are colors of the bands of a common resistor) about to invade your side by pacing downward as they laterally move from side to side. The controls are the number keys of your keyboard which corresponds to the equivalent number code of a band color in a resistor. You have to hit the right color with the correct number key in able to destroy a particular resistor. As the game progresses, the speed of the resistor also increases so you have to be fast in destroying them. The game is perfect for having a relaxation time while mastering the resistor color coding. The download link is located below the photo. Enjoy!
Mediafire Download Link: When Resistors Go Bad
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