Finding Resistance of an electronic component

In summary, the speaker is trying to repurpose a computer fan and wants to add a potentiometer to control its speed. However, they are having trouble finding the effective resistance of the fan and their attempts with an ohmmeter have not been successful. The proper way to find the resistance would be to measure the voltage and current across the fan at the same time. It is also noted that the back emf generated by the motor can affect the current and the measured resistance may not be accurate.
  • #1
MCCCLXXXV
1
0
This may be a really dumb/easy question, but...
I have a computer fan that I'm trying to repurpose. The specs on the fan say DC12V, 0.25A.

I'm trying to model the fan in a circuit diagram because I want to 1) make sure i don't put too much current through it and 2) add a potentiometer to it to control the speed. Now, in order to find the effective resistance of the fan, I thought I would be able to simply use the V=IR equation and solve for R=12/.25=48ohms. But I hooked up an ohmmeter to it and it seemed like the resistance was no where near 48 ohms and jumped around a lot (mostly just went into overflow mode). What would be the proper way to model the resistance of the fan?

Thanks
 
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  • #2
The easy way is to measure the voltage across the fan and the current through the fan at the same time and then divide the voltage by the current. This will not have any correspondence to the value you measure with an ohmmeter.

When a motor is running it also acts a generator and generates a back emf that opposes the flow of current through the motor. The current through the motor will vary with load so any value you measure is only representative of the motor at that voltage and load.
 

Related to Finding Resistance of an electronic component

1. What is resistance in electronic components?

Resistance is a measure of how much an electronic component impedes the flow of electric current. It is measured in ohms (Ω) and is represented by the symbol R.

2. How do you find the resistance of an electronic component?

The resistance of an electronic component can be found by using Ohm's Law, which states that resistance is equal to the voltage (V) divided by the current (I) passing through the component. This can be expressed as R = V/I. Alternatively, resistance can also be measured using a multimeter.

3. Why is it important to know the resistance of an electronic component?

Knowing the resistance of an electronic component is crucial in determining its behavior and how it will affect the overall circuit. It also helps in making sure that the component is not overloaded with too much current, which can cause damage.

4. Can the resistance of an electronic component change?

Yes, the resistance of an electronic component can change depending on various factors such as temperature, material, and applied voltage. For example, as temperature increases, the resistance of a conductor also increases.

5. Are there any methods to reduce the resistance of an electronic component?

Yes, there are several methods to reduce the resistance of an electronic component. One way is to use materials with lower resistivity or increase the cross-sectional area of the component. Additionally, keeping the component at a lower temperature can also help reduce its resistance.

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