Solenoid time constant

Discussion in 'Physics' started by JardaK, Mar 20, 2015.

  1. JardaK

    Thread Starter New Member

    Mar 20, 2015
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    0
    Hello,

    I have a small problem.
    Solenoid has a resistance of 14.2 ohms and an inductance 0.056H is connected in series with a resistance 2.2Ohm
    Thus calculated is the Tau = L / R = 0,056 / (14.2 + 2.2) = 0.0034s
    But the measured value is 0.02s
    The measurement is done on an oscilloscope for resistance.
    Source is a classic laboratory.

    If I measure only air-core coil corresponds to the time constant.
    How is it possible that tau is based on much more?

    Solenoid Type:
    Code (Text):
    1.  http://docs-europe.electrocomponents.com/webdocs/001b/0900766b8001b732.pdf [/ code]
    2.  
    3. Thank you for your response.
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,766
    1,101
    Did you measure with the plunger extended or retracted? Plunger position will probably have a significant effect on inductance.

    Edit: I don't think you should count the 14.2 Ohms as being in series with the coil when calculating Tau. So Tau = 0.056/2.2 = 0.025 s
     
    Last edited: Mar 20, 2015
  3. JardaK

    Thread Starter New Member

    Mar 20, 2015
    3
    0
    Why?
    A formula please?
    Coil having no core has a smaller inductance. This coil inductance and resistance 0.012H and 14.2Ohm
    0.0012 / (14.2 + 2.2) result corresponds approximately
     
  4. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    Where did the inductance value come from?
     
  5. JardaK

    Thread Starter New Member

    Mar 20, 2015
    3
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