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Current and Voltage of Elements of a Circuit with a Solenoid.

  1. Mar 10, 2013 #1
    Ended up figuring out how to solve this problem. I just was not expecting certain parts of the results which lead me to believe I did it wrong.


    1. The problem statement, all variables and given/known data

    2R_switch_2.jpg

    Voltage of battery is 5V
    Resistors are 5 Ohms
    The solenoid has no internal resistance

    1.Need to find V_2 before switch is opened
    2.The current through the solenoid right after the switch has been opened.
    3. The current through R_2 and R_1 right after the switch has been opened.
    4. Voltage across R_1 right after the switch has been opened.
    5. Voltage across R_1 if it was 5 Mohms right after the switch has been opened.

    2. Relevant equations
    V=IR
    Kirchhoff's Loop Rule

    That a solenoid will want to resist any change in current.



    3. The attempt at a solution
    1. The voltage across R_2 will be 5V because the loop that consists of the switch and resistor has to have a voltage drop of 5 V and the resistor is the only element with a voltage drop on that loop.

    2. The current through the solenoid right after the switch is open will be 1 A as the solenoid will want to keep the same current as before.

    3. 1 A as the current will be same as the solenoid.

    4. The voltage drop across both of the resistors will be 5 V. The solenoid will add additional voltage to create the greater voltage.

    5. 5*10^6 V as the current will still be 1 A.


    I know I probably have flawed logic in here somewhere though I just do not know exactly how a solenoid will effect this circuit after the switch is thrown.
     
    Last edited: Mar 11, 2013
  2. jcsd
  3. Mar 10, 2013 #2

    rude man

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    Are you interested in these various V's and i's just after the switch is opened, or for all time after the switch is opened?
     
  4. Mar 10, 2013 #3
    Just after the switch has been opened. Sorry thought I put that in the questions but I must of missed putting that there.
     
  5. Mar 11, 2013 #4

    rude man

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    Everything is correct. Congrats!
     
  6. Mar 11, 2013 #5
    Yeah I ended up getting the answers back and I got a happy suprise when I saw that I was correct. I guess thats why they put the question in the post lab, to show how solenoids can do this.
     
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