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Introduction - Basic Potentiometer Theory • Resistors • Building Potentiometers • Modern Variable Resistive Devices • Applications Modes • The Parts of a Potentiometer • Resistive Elements • Cermet • Conductive Plastic • Hybrid Elements • Terminations • Contacts • Electrical Parameters • Total Resistance • Minimum Resistance • End Resistance • Contact Resistance • Contact Resistance Variation • Equivalent Noise Resistance • Output Smoothness • Adjustability • Temperature Coefficient • Resolution • Conformity • Linearity • Power Rating • Summary of Electrical Parameters • Useful Terms
Power Rating
Power Rating is the maximum heat that can be dissipated by a potentiometer under specified conditions with certain performance requirements. You will recall that heat is the result of current passing through a resistance.
Power is calculated by using one of two equations:
Where P is the power dissipation in watts and R is the total resistance in Ωs, I is the total current in amps flowing through the resistance, and E is the total voltage drop expressed in volts.
Why is power rating an important spec?
The useful life of a given potentiometer is directly related to the maximum temperature allowed in the interior of the unit. Above a certain internal temperature, insulating materials begin to degrade. A maximum power rating indicates to the circuit designer just how much power may be safely dissipated without harm to the device.
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