How to learn resistance power

How to learn resistance power

Any resistor is characterized not only by resistance, but also the maximum disseminated power. If to exceed it, the component can burn down, put the heat out of action the next details or even to cause ignition.


1. That to recognize the minimum power of the resistor which can be used in this place of the scheme by a symbol look at the sign in the center of designation. Capacities from 1 W and are coded by usual Roman figures above. Fractional values are designated so: 0.5 W - longitudinal line, 0.25 W - diagonal line, 0.125 W - two diagonal lines. If use of the wire resistor is obligatory, then instead of a rectangle for it other symbol - the zigzag line near which the text, besides resistance, specified also power is used. Consider that in some countries of the world it is accepted to designate thus any resistors, and not just wire.

2. The way of designation of power on the resistor depends on its type. If it is wire and is executed in the ceramic case, this parameter is specified on it along with resistance the usual text. For example, 5 W for the import resistor, 5 W - for domestic.

3. On domestic small-sized resistors the value of power is given after designation of type and separates from the last a hyphen. The unit of measure at the same time falls, and as that the watt is meant. For example, the MLT-2 resistor is calculated on the maximum disseminated power in 2 W.

4. If the resistor import, and the value of resistance on its case is designated not by figures, but the color code, then data on its power, as a rule, are absent. It is possible to learn it in two ways. In the beginning look at a group container: perhaps, the relevant information is placed on it. If there is no container, or power on it is not specified, compare the resistor on diameter and length to domestic MLT or OMLT of the known capacities.

5. In the absence of any data on the admissible power of the resistor buy the contactless infrared thermometer differently called a pyrometer in pharmacy. At the enterprise it is possible to use a pyrometer of industrial function also. Connect the resistor to the adjustable power supply via the ampermeter, and parallel to it attach the voltmeter. Smoothly increasing tension from zero (considering lag effect of a component), achieve that temperature of the case of the resistor was 50 - 60 degrees. Transfer indications of the voltmeter and the ampermeter to the SI system and increase at each other. You receive value of the power disseminated on the resistor in watts.

Author: «MirrorInfo» Dream Team