 # Adjustable Resistors - Power Ratings vs Resistance Value

A recent question that came in was regarding Adjustable Power Resistors and how the power rating is affected by the change in resistance. So does the change in resistance cause a change in power? The short answer, yes. Resistors are passive elements that introduce resistance to the flow of electric current in a circuit. Ohm’s power law states P=R·I²

Lets take a look at Vishay part AVT10006E1K000KE. This is a 1.0K OHM 100W Adjustable Power Resistor. Now assuming your current will remain constant in your circuit, the power of the resistor is directly proportional to the resistance given to the resistor via the adjustable band.

For simplicity lets assume you have a current of 0.316A in your circuit, then:

• If you set the resistor to 1.0K Ohms, you’ll obtain 1.0K Ohm · 3162A ~ 100W (Max Resistance would be Max Rated Power)
• If you set the resistor to 500 Ohms, you’ll obtain 500 Ohm · 3162A ~ 50W
• If you set the resistor to 250 Ohms, you’ll obtain 250 Ohm · 3162A ~ 25W

Applicable Part Numbers