- #1
fog37
- 1,568
- 108
Hello Forum,
the law of electromagnetic induction states that a time-changing current causes a back (counter) emf in an inductor. The back emf opposes the change in current by generating an induced current I_ind.
If dI/dt>0, the induced current is opposite in direction to the main changing current. If dI/dt<0, the induced current is in the same direction as the changing current trying to keep it going.
That said, I am confused about the polarity of the emf (please see figure below): the emf points to the left and that makes sense since the induced current must oppose the increasing current. A current always moves from high potential to lower potential.
But why is V_ab positive and directed opposite to the emf? Point a has a higher potential than point b. Current usually goes from high potential to lower potential (unless it is traversing the inside of a battery)...
Thanks,
fog37
the law of electromagnetic induction states that a time-changing current causes a back (counter) emf in an inductor. The back emf opposes the change in current by generating an induced current I_ind.
If dI/dt>0, the induced current is opposite in direction to the main changing current. If dI/dt<0, the induced current is in the same direction as the changing current trying to keep it going.
That said, I am confused about the polarity of the emf (please see figure below): the emf points to the left and that makes sense since the induced current must oppose the increasing current. A current always moves from high potential to lower potential.
But why is V_ab positive and directed opposite to the emf? Point a has a higher potential than point b. Current usually goes from high potential to lower potential (unless it is traversing the inside of a battery)...
fog37