Resistor, capacitor or inductor

Discussion in 'Homework Help' started by iamforyou2, Jan 4, 2007.

  1. iamforyou2

    Thread Starter New Member

    Nov 23, 2006
    3
    0
    Hi,
    I have been given a selaed box to find out whether the hing in it is resistor, inductor or capacitor by performing diefferent tests, could any one please help me ith different kind of tests on box so i can find out what actually is in the box.

    the box have got 2 terminals

    any help wil be appereciated
     
  2. Dave

    Retired Moderator

    Nov 17, 2003
    6,960
    143
    I assume you have access to a signal generator and a two channel oscilloscope. If so, connect the signal generator to the two terminals and pass a 1Vp-p sine wave through the component. Use the oscilloscope to measure the current through the component and the voltage across the component.

    If the component in the box is a resistor, the current and voltage will be in phase.

    If the component in the box is a capacitor, the current will lead the voltage by 90 degrees (approximately).

    If the component in the box is an inductor, the current will lag the voltage by 90 degrees (approximately).

    Remember when measuring current, place the scope in series with the component, and when measuring voltage place the scope in parallel with the component.

    Dave
     
  3. iamforyou2

    Thread Starter New Member

    Nov 23, 2006
    3
    0
    thanks alot dave

    if we take the discussion further, lets say that the mystery component is RC, or RL .
     
  4. Dave

    Retired Moderator

    Nov 17, 2003
    6,960
    143
    If the mystery component is a series RC, then the current will still lead the voltage but by an angle of less than 90 degrees. Conversely, if the mystery component is a series RL, then the current will still lag the voltage but by an angle of less than 90 degrees. This is because the voltage drop across the resistor is parallel to current flowing through it, where as the voltage drop across a capacitor or inductor is orthogonal to the current flowing through it. Therefore, for RC and RL arrangements the measured phase difference between the current and voltage is deduced via a phasor relationship, ref RC Circuits and RL Circuits.

    Dave
     
  5. iamforyou2

    Thread Starter New Member

    Nov 23, 2006
    3
    0
    Cheers man
    you have really solved my problem
     
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