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Introduction:
Resistor is a passive, two-terminal electronic component, that limits the flow of electrons, inside a circuit.
The value of the resistor is called its resistance.
Ohm is the unit of resistance.
For higher values, we use Kilo ohm, Mega Ohm.
Higher the value of resistance, the lower the current can pass through it.
This is the symbol for the fixed value resistor, and it is the symbol for the variable value resistor.
Resistor is used to limit the flow of current in a circuit.
For example, if we want to glow an l e d using a 5V battery, then we must know the turn on voltage and current consumption of that l e d.
Suppose, this LED needs 2 volt to turn on, and 15 milliamperes current to operate.
So, to operate this l e d using a 5-volt battery, we need a resistor which can drop 3 volts across itself, and allow to pass only 15 milliamperes of current through it.
To calculate the value of the resistor, we will use the ohm’s law.
V = I R
So, in this formula, we will put the value of voltage v, 3 volt and the value of current I, 15 milliamperes, then the value of r will come out to be 220 ohms.
Now we will calculate the desired power rating of the resistor by using the formula, p = v i.
It is 45 milliwatts.
So, we must use the resistor, which can bear at least 45 milliwatts of power dissipation.
When we connect several resistors in series, then the final value is the sum of all the resistors.
If we connect, 1, 2 and 6 kilo ohms resistor in series, then the final value will be 9 kilo ohms.
When we connect them to a power supply, then same current will pass from each resistor, but the voltage drop across each resistor will be different.
If we connect them in parallel, then the final value of resistor can be derived from this formula.
In parallel connection voltage drop across each resistor will be same but the current passing from each resistor will be different.
This configuration of resistor is called, voltage divider.
This configuration is used to drop the voltage.
By using this configuration, we can set various values of voltage at its output.
For example, if we assume that the value of resistor r 1 is 1 kilo ohm, the value of resistor r 2 is 9 kilo ohm and the input voltage is 5 volts, then the value of output voltage can be calculated using this formula, it will be 4.5 volt.
By using the same formula, the values of the resistors r 1 and r 2 can be derived, if the output and input voltage are known.
If we use a variable resistor in place of r 2, then the output voltage will change with the change in value of resistor r 2.
There are many types of sensors, whose internal resistor value depends upon the environmental conditions, such as the value of a thermistor varies with temperature.
If we use a thermistor in place of r 2, then the value of the output voltage, will change along with the value of the temperature.
This principal is used in a digital thermometer, to measure the value of temperature.
The classification of resistors is done on many grounds.
On the basis of mounting, resistors are of two types s m d surface mounted resistors and p t h plated through hole resistors.
On the basis of value, fixed value and variable value resistor.
On the basis of orientation, radial and axial resistor.
On the basis of construction, metal film, carbon film, wire wound resistor.
Apart from this, these sensors are also a form of resistor, they change their resistance when the temperature is changed, or when the force is applied or when it is folded.
The multimeter can be used, to measure the value of the resistor.
Value of the resistor can also be derived from its color code.
Resistor has a specific number for each color.
Like number zero is of black color, number one is of brown color.
Now, let’s find the value of the first resistor, given in the chart.
The first color in this resistor is red, so the first number is two, the second color is purple, its number is seven, third color is of multiplier, the third color is yellow and its number is 4, and will be write as 10000, 4 zeros after 1. So the value of the resistor, is 27, multiplied by, 10000, or, 270 kilo ohms.
Last color is of tolerance.
Resistors can have up to 6 color bands.
First 3 colors, indicates resistor value, and the rest colors indicates the characteristics of the resistor, like tolerance and temperature coefficient.
In s m d resistors, the values are printed in the form of numbers, such as 472 means, 47 multiplied by 100, and it is 4.7 Kilo ohms.
Resistors are made by various ways, and have different names too, such as carbon composition, carbon film, metal film, wire wind etc.
In this chart, you can find out the difference in resistors made in all these ways.
This was some basic information about resistor. I hope you enjoyed the video. Thank you so much.
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