#76 - Three Ways Ohms can Lie

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  • เผยแพร่เมื่อ 24 ม.ค. 2025

ความคิดเห็น • 10

  • @TheTechCircuit
    @TheTechCircuit  ปีที่แล้ว +2

    Ohms don't lie, but don't always give you the whole story. This video is intended for experienced or supervised technicians. Always take appropriate safety precautions when dealing with live circuits. For informational purposes only. Utilize the concepts in this video at your own risk. The Tech Circuit or Steve Morrison assumes no responsibility or liability for any errors or emissions in the content of this video. The information contained in this video is provided on an as is basis with no guarantees of completeness, accuracy, usefulness, or timeliness.

  • @uxwbill
    @uxwbill ปีที่แล้ว +1

    This video explained something I had wondered but not really thought about or checked against a schematic -- why some gas stoves leave their igniter running even after the burner was lit.

  • @TheTechCircuit
    @TheTechCircuit  ปีที่แล้ว

    I'm forcing the centrifugal switch inward with my left hand in the beginning of the video so as to disengage the start winding. Only the main (run) winding is being statically measured - as stated in the introduction. That's the same winding the current flows through when the motor is running at normal RPM.

  • @kabandajamir9844
    @kabandajamir9844 11 หลายเดือนก่อน

    Please make a video on metal oxide varistor testing

  • @DrHarryT
    @DrHarryT ปีที่แล้ว +2

    Ohms law never lies, that's why they call it "Law" anyone who is worth their weight know that there are operational variables with respect to a device under load. For example, an incandescent lamp when the resistance is measured and the math [Ohms Law] is applied would indicate that the lamp will draw much more current than it actually does in operation. This is because as the filament get hotter its resistance goes down.
    In the case of the motor there is inductance and eddy currents and impedance that must be taken into consideration. Try locking the motor shaft and depressing the centrifugal switch into the run position and then measure the current, it then probably would draw 34A.

    • @TheTechCircuit
      @TheTechCircuit  ปีที่แล้ว

      Yep. That was the point of the video. To explain all that, and what the colloquial term "ohms lie" means.

  • @mohnewyork1082
    @mohnewyork1082 ปีที่แล้ว

    So mean to test this components you have to energize them and measure after few minutes measure ohm's? And use ohms low ?

    • @TheTechCircuit
      @TheTechCircuit  ปีที่แล้ว +1

      Some components, like those highlighted in the video act differently when energized vs. when you test them with an ohmmeter. In such cases, their behavior can be better determined by using current draw while energized.

  • @paradiselost9946
    @paradiselost9946 ปีที่แล้ว

    theres another factor with the motor... BEMF. more pronounced if it was a brushed universal motor, admittedly.
    um... theres another strange effect ive seen with resistors, and that was on the gate of FETs...
    as per datasheet, you throw in a 4R7, and thats cool. scope the signal, and you see the ideal "square wave" with no ringing.
    reduce that resistance, and the ringing increases until you overdo the maximum ratings... oops.
    but increase it... 10R... start seeing that square wave developing a curve...
    and then, at say, 27R... the resistor starts burning out... woah woah woah! gotta go from 1W to a 5W! wtf?
    and then start exceeding 100R, and you can reduce that wattage again... (it does depend on the fet of course, take all numbers with a grain of salt...)
    it makes sense when you start thinking about it...
    at a low resistance, there may be a large current, gate charge... but the voltage drop across the resistor and the power dissipated is quite low.
    as it increases, the voltage drop and dissipation increases...
    until finally, it reaches a point that its simply limiting the current and at that point, dissipation reduces again.

  • @mikeadler434
    @mikeadler434 11 หลายเดือนก่อน +1

    👍👍