To calculate the value of a resistor from colour codes.
Then, First, you have to locate the Tolerance band.
The tolerance band mostly in most of the resistors is made from either gold colour or silver colour.
Then you need to look at the next band which tells you the multiplier.
Then you need to look at the opposite end of the resistor and note down the colour in order till the multiplier.
The first band from the left gives us the first digit.
The next band gives the next digit.
A resistor is an electronic component that offers resistance in the flow of current. The practical resistor has a slight shift in its values from the ideal counterparts.
Not all the values of the resistor are available in the market. There is a certain number that is chosen and is readily available. If a particular value is to be achieved then a combination made from the selected resistors is to be used.
An ideal resistor follows Ohm’s law.
A practical resistor changes its value if the surrounding temperature, pressure and changes in mechanical dimension etc. Though there are very nominal changes yet they differentiate the ideal resistor from the practical counterpart.
The resistors value is generally marked on the surface. If the resistor is big, standard values along with manufacturing company seal are also printed on top of it.
For very small resistors; either colour bands or some code is written on top of it. As the size goes on decreasing the surface area becomes small and reaches a point where it is not feasible to print anything that can be visible to the naked eye. Then the values are written beside the component.
There are two types of resistors.
It is important to consider the power dissipation of a resistor. Since resistor obstructs the flow of current. The obstruction causes a buildup of energy which needs to dissipate. If this energy is not released then it will burn the resistor or permanently change its resistance values. So resistors use heat to dissipate the energy.
for example:
Let’s consider an 8-ohm resistor that resists the flow of current.
A voltage source of 9V has connected across. The 8-ohm resistor drops the voltage from 8V to 0V. Blocking a significant portion of voltage that is 8V.
and Let’s say the current flowing in the circuit is one Ampere.
So the resistor needs to dissipate 8W of energy.
Now you need to select a resistor that can dissipate more than 8W of energy. and the next best option is to use a resistor of 10 watts.