It is a passive element the most important function of resistor is to resistance the flow of current. The property of a resistor is know as resistance.
A resistor can be used as a load, potential divider and also known as biasing element in different circuits. It also act's as a filter and timer in combination with capacitor. Resistor are basically available in two types viz:- (fixed resistor) & ( variable resistor) . Now a days a resistor are availed in a large variety of types and sizes each type has specific advantage.
A resistor will have three main specifications that are to be considered they are,
1.Resistance value
2.Tolerance
3.Power rating
Step by step so,
1. Resistance value:-
It gives the resistor 'R' ohm's it's value is either printed or colour coded over the body depending upon the type of resistor in general resistance from 1 ohm to many mega ohm are available.
2. Tolerance:-
It gives the variation of resistance value from the indicate value it is generally expressed in percentage and tolerance means in manufacturing process is not exact equal value is called tolerance.
3. Power rating:- (capacity of device)
The resistor with power rating ranging from 0.1 watt's to 100 of watt's are available. In resistor the maximum weight less capacity and power rating is depends on a size of resistor. However, there are some other specifications that are to be considered while selecting a resistor they are,
4.Temperature coefficient of resistance:-
It gives the variation of resistance with change in temperature it is usually measured with reference to resistance at 25°c.
Negative temperature coefficient and positive temperature coefficient are depends resistor in temperature.
5.voltage coefficient:-
It is measured as the change resistance of a resistor with a change in the applied voltage.
6. High frequency performance:-
Generally, the resitors with lower resistance values will have better ( high frequency performance)
7. Noise figure:-
Noise in resistor is of two types :-
1. Themal agitation noise
2. Current noise wire wound resistor exhibit little current noise when compared with carbon composition resistor.
8. Stability:-
If it is used for a long period under atmospheric conditions and it's value measured at room temperature is nearer to initial measured value. Carbon film, metal film, wire wound resistor, are more stable than carbon composition resistor
9. Size, shapes and leads :-
Resistor are available in different sizes (small, big) and shapes (rod, disc, washer) with different types (axial, radial, lug) of leads or terminals. The selection of particular type of resistor depends on the requirements.
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