When you learn about electricity, you actually learn about two materials the Conductors and the Insulators. The conductors such as the metals that let the electricity to flow from them; and the insulators such as the materials that not allow electricity to pass from them. But is it as simple as it sounds!, any substance will conduct electricity if provided with a big enough voltage across it, even in air, which is normally an insulator suddenly becomes a conductor if provided with large enough voltage across it, like in lightning, the air becomes conductor. Rather than talking about conductor and insulator we should talk about Resistor because it is the property that appears in both the conductors and the insulators. A conductor has low resistance, while the insulator has very high resistance or it may be called as infinite resistance.
What is resistance?
The internal blockage in the flow of electrons is called resistance. Resistance is the property of material from which the conductor is made, but to provide an extra resistance in any circuit, resistor is used.
What is resistor?
Resistor is a material or an element which is used to provide an extra required resistance in the circuit. This is all little undefined thing for a subject like electronics, which requires the overall control on electric circuit currents. That’s why we define resistance in simple words to make it understand what actually it is.
Why We Use Resistor?
For example: there is a circuit having battery of 500 Volts and maximum current supply capability of 1 ampere. Now how can you make 1 amp flow from the circuit?
Since we all know the basic relationship of Ohms law V= I x R
This implies that R = V/I =500/1;
This implies that R = 500 ohm
So we require a resistor of 500 ohms to produce 1 amp.
Actually by increasing the resistance we actually limit the total current.
For example if we increase the resistance from 500 ohm to 600 ohm then I=V/R = 500/600 = 0.833 Ampere. This means the battery is of total 1 ampere capacity, but by increasing the load we actually limit the total current.
One thing is noticeable that in above circuit resistor is used as a LOAD. Yes resistor is used in electrical and electronic circuits as a load and as a protection as well. If we don’t add resistor of any ohms in above example, then actually we are short circuiting it that cause a heavy flow of current at a time causes burn of circuit. So to protect the battery as well, we are using resistor.
In some cases we use resistor to protect the main load.
For example we have battery of 5 Volts and a LED as load of 3 Volts are connected in parallel, Now what do you think, what happen if we switch the circuit ON?
Since the supply is of 5 volts and the load is of 3 volts, so battery supply the current according to its voltage (V=IR) Now here we have to use resistor in series with the load, since the voltage distributes in series, so the LED (Load) will not get the overall voltage of 5 volts and will not damage.
How Resistor Works?
People who make electric or electronic circuits to do particular jobs often need to introduce precise amounts of resistance. They can do that by adding tiny components called resistors. A resistor is a little package of resistance: wire it into a circuit and you reduce the current by a precise amount. From the outside, all resistors look more or less the same. As you can see in the top photo on this page, a resistor is a short, worm-like component with colored stripes on the side. It has two connections, one on either side, so you can hook it into a circuit.
What’s going on inside a resistor?
If you break one open, and scratch off the outer coating of insulating paint, you might see an insulating ceramic rod running through the middle with copper wire wrapped around the outside. A resistor like this is described as wire-wound. The number of copper turns controls the resistance very precisely: the more copper turns, and the thinner the copper, the higher the resistance. In smaller-value resistors, designed for lower-power circuits, the copper winding is replaced by a spiral pattern of carbon. Resistors like this are much cheaper to make and are called carbon-film. Generally, wire-wound resistors are more precise and more stable at higher operating temperatures.