1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Archived Lenz' Law Scenarios for two wires with varying distance between them

  1. Aug 3, 2014 #1
    1. The problem statement, all variables and given/known data
    2h5ivkp.png

    For each of the following scenarios, predict the direction of the induced current ( c-to-d;
    d-to-c; NO INDUCED CURRENT) in the second set of coils, N2.


    1. The current, I1, direction ‘a-to-b’, is increasing rapidly. The coils remain stationary.
    2. The current, I1, direction ‘a-to-b’, is increasing slowly. The coils remain stationary.
    3. The current, I1, direction ‘b-to-a’ is constant; the coils, N2, are moved coaxially and slowly toward the stationary coils, N1 .
    4. The current, I1, direction ‘a-to-b’ is constant; the coils, N2, are moved coaxially and rapidly away from the stationary coils, N1 .
    5. The current, I1, direction ‘b-to-a’ is constant ; the coils, N2, are moved slowly and laterally, maintaining the separation, L, between the planes of the coils .



    2. Relevant equations

    flux.gif
    12138.png
    magcur5.gif

    3. The attempt at a solution

    1. When I increases in one direction on one wire, Lenz' law implies that the other wire will have an increase in current in the opposite direction in order to maintain the net flux. Therefore a rapid increase in current from a to b will induce a current from d to c rapidly.

    However the question does not ask for the magnitude, only the direction, so the fact that the change is rapid or slow does not affect our answer, right?

    2. Rate of change in flux will affect magnitude but not direction so the answer is once again, D to C.

    3. Using the equations in the pictures above, I explained magnetic flux is proportional to (1/L) with L being the distance between wires... So If L decreases, flux increases. Lenz' law says an increase in flux will result in an induced emf in the opposite direction.

    Therefore if the current is moving from B to A while L decreases, the induced emf will be from C to D.

    4.
    Increases in L will result in decrease in flux and induced emf in the same direction. Since current is fro A to B this will be C to D

    5.
    The separation L is maintained so there should be NO change in flux, right?
     
  2. jcsd
  3. Feb 28, 2016 #2

    Merlin3189

    User Avatar
    Gold Member

    1-4 seem comprehensively answered and I agree.
    5 although L is fixed, the separation of the coils is increasing, so the flux linkage is decreasing and the induced voltage is D to C.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Lenz' Law Scenarios for two wires with varying distance between them
Loading...