Direction of the induced current and polarity

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SUMMARY

The discussion focuses on determining the induced electromotive force (emf) and its polarity at time t = 0 using Lenz's law. The calculated value of Vemf is -188.5 V, indicating that the induced current flows in a direction that opposes the increase in magnetic flux, which is positive at that moment. The confusion arises from the relationship between current direction and potential difference, leading to the conclusion that terminal 2 is at a higher potential than terminal 1, contrary to the participant's initial assumption about conventional current flow.

PREREQUISITES
  • Understanding of Lenz's law and its application in electromagnetism.
  • Familiarity with the concept of electromotive force (emf) and its calculation.
  • Knowledge of magnetic flux and its time derivative, dΦ/dt.
  • Basic principles of electric potential and current direction (conventional current vs electron flow).
NEXT STEPS
  • Study the derivation and applications of Lenz's law in various electromagnetic scenarios.
  • Learn how to calculate magnetic flux and its changes over time in different configurations.
  • Explore the differences between conventional current and electron flow, particularly in circuit analysis.
  • Investigate real-world applications of induced emf in generators and transformers.
USEFUL FOR

Students of physics, educators teaching electromagnetism, and anyone seeking to deepen their understanding of induced currents and their implications in electrical circuits.

fishingspree2
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Homework Statement


http://img805.imageshack.us/img805/6030/82154948.png
Find Vemf (between points 1 and 2) and it's polarity at t = 0.
I have omitted details because my question is specifically on the polarity.

Homework Equations


Lenz's law:
An induced electromotive force (emf) always gives rise to a current whose magnetic field opposes the original change in magnetic flux.

Vemf = -dΦ/dt

The Attempt at a Solution


This is a worked out example in my textbook. We first find the flux Φ and Vemf which are function of time. We compute dΦ/dt at t = 0. Then Vemf = -dΦ/dt.

We find that dΦ/dt > 0, so the magnetic field B is increasing. To counter-act this change, I must be in the direction given in the picture. Everything is ok at this point.

Now here is where I get lost. My textbook says:

At t=0, dΦ/dt > 0 and Vemf = -188.5 V. Since the flux is increasing, the current I must be in the direction shown in the figure in order to satisfy Lenz's law. Consequently, terminal 2 is at a higher potential than terminal 1 and Vemf = V1 - V2

I thought I always is from the higher potential to the lower potential. Which should make terminal 1 at a higher potential than terminal 2 considering the direction of I. It seems like the textbook have it reversed.

What am I missing?
 
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Is it a matter of conventional current vs electrons flow?
 

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