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Electric potential across a simple circuit

  1. Sep 30, 2012 #1
    1. The problem statement, all variables and given/known data
    Consider the image and assume that the switch has been open for a long time. Note that the switch is supposed to be between the battery and the resistor on the top straight segment, which is not shown in the image.

    http://www.sciencebuddies.org/science-fair-projects/project_ideas/Elec_img160.jpg [Broken]

    Also consider the initial electric potential to be V_o

    a) What is the electric potential before and after the battery, switch and resistor?
    b) What is the potential across the resistor
    c) What is the electric potential at all points (i.e before and after the battery, switch and resistor) immediately after the switch is closed?
    d) What is the electric potential difference across the resistor immediately after the switch is closed
    e) After a long time after the switch has been closed, what is the electric potential at all points and what is the electric potential difference across the resistor?

    2. Relevant equations

    Kirchhoff's loop law:

    ΔV_loop = 0

    3. The attempt at a solution

    I am having some trouble understanding the concept and I am looking for a second opinion towards my responses toward these question.

    a) Since the current is broken, there is no change in electric potential (no voltage drop) therefore, before and after the battery, switch and resistor should all be 0

    b) Likewise, the electric potential difference across the resistor should be zero

    c) Immediately after the switch is closed, from the battery to the point before the resistor, the electric potential should be equal to V_o. After the resistor to the point back to the battery, the electric potential should be 0

    d) The electric potential difference will be -V_o

    e) After a long time, there should be no change, therefore the answers should be similar to c and d.

    Thanks for the help.
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Sep 30, 2012 #2

    gneill

    User Avatar

    Staff: Mentor

    ...snip...
    Potential with respect to what? You need to define a reference point with respect to which potential is to be measured (define two points and then determine the potential difference from one to the other). What's your point of reference for the above? Perhaps it's the bottom (negative terminal) of the battery?
     
    Last edited by a moderator: May 6, 2017
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