how to find out current through inductor in DC circuit?

Discussion in 'Homework Help' started by vead, Aug 4, 2016.

  1. vead

    Thread Starter Active Member

    Nov 24, 2011
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    Hello
    I need help to understand the basic concepts of inductor. Suppose 1h inductor is connected across 10v battery. Inductor is non linear element it change the value of current over the time. How to find out current through inductor?
     
  2. Ramussons

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    May 3, 2013
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    Any problem using a Ammeter or Millammeter? :confused:
     
  3. Kermit2

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    Feb 5, 2010
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  4. vead

    Thread Starter Active Member

    Nov 24, 2011
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    I can use the multimeter but I just want to find out using the formula.
     
  5. Alec_t

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    Sep 17, 2013
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    E=10, L=1. Use the formula to find di/dt.
     
  6. vead

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    Nov 24, 2011
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  7. DickCappels

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    Aug 21, 2008
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    You can use the formula for LR circuits. Use an ohmmeter to find the resistance of your inductor and use that value as R in the formula.
     
  8. vead

    Thread Starter Active Member

    Nov 24, 2011
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    So I don't know time and I have find out the current. Should I have to suppose the time
     
  9. DGElder

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    Apr 3, 2016
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    The current will rise linearlly at 10A per second, until the universe explodes. At least that is what would happen if you had ideal inductor and voltage source. Real components have resistance, use the tutorial math. You will need to know the source output resistance and inductor resistance to calculate the current.

    Don't try hooking that up, you will pop a fuse or drain your battery.
     
    Last edited: Aug 4, 2016
  10. Alec_t

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    di/dt means 'the rate of change of current with time'. If you found one (non-zero) value of the current that must have been at one specific time, unless the current had reached a value limited by the resistance of the inductor.
     
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  11. vead

    Thread Starter Active Member

    Nov 24, 2011
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    given
    V=10v, L=1h, di/dt=10A/s
    Voltage drop across the inductor is
    v=Ldi/dt
    v=1*10=10v
    Voltage drop across the 1h inductor is 10 volt
    Still the current is unknown
     
  12. crutschow

    Expert

    Mar 14, 2008
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    If you can't understand what is being said to you then how can we help? :confused:

    The current isn't unknow, you just haven't calculated it.
    The current in an inductor continually increases with time after the application of a DC voltage according to (di = Vdt/ L).
    This gives the increase in current with time.
    To find the current at any point in time you multiple the time by V/L
    Thus, in you example, at 5 seconds the current would be 5s * 10A/s = 50A
    The maximum current in the inductor after a large period of time is limited by any resistance in the circuit and will settle at a value of V / R.

    If you can't understand that, than I don't know what further can be said. :rolleyes:
     
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  13. vead

    Thread Starter Active Member

    Nov 24, 2011
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    Now I can understand and I can find out the energy stored in inductor
    E=1/2Li*i
    E=0.5*1*50*50
    E=1250 joules

    Power P=Li*di/dt
    P=1*50*10
    P=500W
    Is this calculation is correct?
     
  14. Papabravo

    Expert

    Feb 24, 2006
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    That equation is not true when V and i have reached their steady state values. As you know, steady state means nothing is changing, and so di/dt will be zero for all future time and the value of L will be irrelevant, thus:

    P_L\;=\;i^{2} \times R_L\;=\;\left(\frac{V_L}{R_L} \right) ^2\times R_L
     
    Last edited: Aug 4, 2016
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  15. vead

    Thread Starter Active Member

    Nov 24, 2011
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    Now I just connected the AC supply across 1h inductor
    If the applied voltage is 10v AC with 60Hz signal than I am trying to find out current through inductor
    Inductive reactance XL=2*3.14*f*L
    XL=2*3.14*60*1
    XL=377.11ohms
    Now I know the Inductive reactance than I can calculate current through indctor
    I=V/XL=10/377.1=0.0265A
    I just wanted to know that how can we determine current through the inductor in AC and DC circuit
    So again, please check my work and if there is any mistake tell me
     
  16. DGElder

    Member

    Apr 3, 2016
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    That is correct.
     
  17. WBahn

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    Mar 31, 2012
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    An inductor is NOT non-linear element.

    What is your math background like? Have you seen any calculus yet? Do you understand exponentials and logarithms?
     
  18. vead

    Thread Starter Active Member

    Nov 24, 2011
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    Power in AC circuit
    P=i*i*XL
    P=0.265*0.265*377.11
    P=0.2648w
    How to calculate energy in AC circuit
     
  19. WBahn

    Moderator

    Mar 31, 2012
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    What energy are you trying to calculate? There are different energy questions that could be asked.
     
  20. vead

    Thread Starter Active Member

    Nov 24, 2011
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    OK my mistake
    Resistor, capacitor and inductor are linear element
    Diode transitor are non linear element
     
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