Resistors Specification
Points : Resistors Specification
The resistors are, specified in terms of their resistances values, tolerance, power rating
and thermal stability. By tolerance, we mean the allowed variation permitted in the
normal or marked value of the resistors.
It means that the actual value of the restore may be either greater or smaller than that of the indicated value, by a factor given by the specified tolerance. Thus resistors are manufactured with a specified tolerance. For examples, a 5000 omega resistor with a tolerance of± 10% will have an actual resistance value anywhere between 4500 omega and 5000 omega or in other words 500 omegas greater or smaller than the rated value.
The power rating of a resistor is given by the maximum wattage it can dissipate, without excessive heating. Since the power rating is proportional to the square of the current, therefore current must not be higher then it’s safe value. If the current exceeds the safe value, the resistance will bum out. Usually, carbon composition resistors will fail, if operated at or near the rated power values. In this gradually to a much lower amount of resistance. This causes an improper operation of an. electronic circuit particularly in amplifier. Thus in order to increase the life of resistors, these must be used at much less power than their rated values. A stand practice is to use a power dissipation of about half of the rating of the resistors.
It means that the actual value of the restore may be either greater or smaller than that of the indicated value, by a factor given by the specified tolerance. Thus resistors are manufactured with a specified tolerance. For examples, a 5000 omega resistor with a tolerance of± 10% will have an actual resistance value anywhere between 4500 omega and 5000 omega or in other words 500 omegas greater or smaller than the rated value.
The power rating of a resistor is given by the maximum wattage it can dissipate, without excessive heating. Since the power rating is proportional to the square of the current, therefore current must not be higher then it’s safe value. If the current exceeds the safe value, the resistance will bum out. Usually, carbon composition resistors will fail, if operated at or near the rated power values. In this gradually to a much lower amount of resistance. This causes an improper operation of an. electronic circuit particularly in amplifier. Thus in order to increase the life of resistors, these must be used at much less power than their rated values. A stand practice is to use a power dissipation of about half of the rating of the resistors.
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