subject: What are resistors? [print this page] What are resistors? What are resistors?
Resistors are those small wires that have that block like thing in the center that looks like a wooden small knob with a bunch of stripes on it. It is as small as a LED light bulb and is actually attached to one. Resistors are elements of electrical networks and electronic circuits and are everywhere in most electronic equipment. Sensible resistors are not hard to find and are actually made of various compounds and films, as well as resistance wire (wire made of a high-resistivity alloy, like alloy).
I am sure that by now you are wondering why such a small piece of wire is so important, well this is because they actually contribute to the low voltage need of the LED light. The resistors are specially designed to be installed on LED lights to reduce the voltage, and to limit the current that travels to the LED it regulates the current to keep it at a safe value. So in short, the resistor helps give the LED light the convenience and the saving value that we all know and love.
Resistors can be incorporated into hybridand 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 dissipated their power. This is important because if the average power dissipated is more than what the resistor can safely dissipate then the resistor may separate from the nominal resistance and become damaged, overheated or worse cause the LED to fail altogether. Excessive power dissipation may also raise the temperature of the resistor to the point where it can burn out; this may cause a fire in its surrounding materials. Good thing there are flameproof resistors that fail before they dangerously overheat. We must also take note that the normal power rating of the resistor is not the same as the power that it can safely dissipate during its practical use. Factors will also affect its performance; some are air circulation and proximity to a circuit board, its ambient temperature and other factors, some of which may reduce the acceptable dissipation rate significantly.
The value of the resistor can be measure with the use of an ohmmeter; this may also be one function of a multimeter. These are just probes that can test the leads that connect to the resistor. Measuring the low-value resistors, like the fractional-ohm resistors, with their acceptable accuracy requires four-terminal connections. One pair of terminals applies the known calibrated current to the resistor, while at times the other pair senses the voltage to drop across the resistor. Most laboratory test instruments have the spring-loaded pairs of contacts, with the near contacts electrically stable and isolated from each other. Some of the newer electronic multimeters have four terminals on their panels, meaning they generally use special test leads. These comprise four wires in all, and make use of the special test clips with jaws that are insulated away from each other of course. One of the jaws provides the measuring current while the other jaw senses the voltage drop. Once the resistance is in it is then calculated using Ohm's Law. Resistors can also be used in a series or in a parallel circuit; it still has the same function.
No matter what kind of resistor that is, the bottom line is that Resistors restrict the flow of electric current to the LED or whatever is connected to the resistor. When picking out a resistor just keep in mind the kind of circuit you have and what device would you like to connect the resistor to. If you still have a hard time picking the resistor then go right ahead and ask any electrician for some assistance or do some research on your own, it pays to know your stuff.
