All about Resistors

What is a Resistor?

Answer: These are very simple element except they have a colour coding on their body to mention how much resistance they have. The work of a resistor is very simple, �TO RESIST�. And of course it resists current (electricity).  

It is a two-terminal electronic component that implements electrical resistance as a circuit element. The current flowing through a resistor is in a direct proportion to the voltage across the resistor's terminals. 

Units:

The ohm (symbol: O) is the SI unit of electrical resistance. It was named after Georg Simon Ohm.  An ohm is equal to a volt/ampere.

 

Series and parallel resistors:

When two or more resistors are connected one after another is called series connection and when two or more resistors are connected in two particular node then it�s called parallel connection. In a series configuration, the current will be same for all of the resistors, but the voltage across each resistor will be proportional to its resistance. The voltage seen across the circuit is the sum of those voltages. So, the total resistance will be the sum of those resistances:

 

In a parallel configuration. all of the resistors will have same potential difference or voltage. But the current through them will b added. Thus, the conductances of the network is defined by the conductances of the resistors. So, the equivalent resistance (Req) can be found as:

 

Two vertical lines "||" are used to show the parallel connection as a simplified notation. If two resistors R1 and R2 are in parallel then we can easily calculate:

Power dissipation:

If we want to find the power a resistor dissipates in a circuit, we can calculate it as follows:

where, P is power, I is for current, V is for voltage, R is for resistance.

Each resistor have a certain power rating. If the average power dissipated in a circuit by a resistor crosses the power rating then the resistor may be damaged. Resistors also have a temperature coefficient. If the resistors power dissipation is high then the temperature will rise too much that it can burn the circuit board or other elements adjacent to it. It may also cause fire. So we have to be careful about choosing the right power rating of resistor before connecting the resistor to our circuit board.

To know about COLOR CODE of RESISTOR click here.