EMF v time graph vs change in flux v time

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Homework Help Overview

The discussion revolves around understanding the relationship between an induced electromotive force (emf) and the change in magnetic flux over time, as presented in a problem from the 2007 HSC. Participants are examining how the emf graph corresponds to the flux graph, particularly why the emf can be at a maximum even when the change in flux is increasing or decreasing.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are exploring the mathematical relationship between emf and magnetic flux, questioning the interpretation of the graphs provided. There is discussion about the conditions under which the emf reaches its maximum and the implications of the graph's steepness.

Discussion Status

Some participants have offered insights into the mathematical definition of emf and its relationship to the rate of change of flux. There are differing interpretations regarding the significance of vertical lines in the graph and the nature of maximum and minimum values in this context. The discussion is ongoing with various perspectives being explored.

Contextual Notes

The original poster indicates a lack of understanding regarding the problem setup and the graphs, suggesting that there may be assumptions or definitions that need clarification. The nature of the graphs and their representation in the problem is also under scrutiny.

alv
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I'm actually a teacher and I can't explain this problem from the 2007 HSC. I've attached a copy of the question and the two graphs. The question shows a graph of change in magnetic flux vs time and asks you to choose which graph of induced emf best fits it. I don't understand why the induced emf is at max even while the change in flux increases (or decreases).

I've searched for help on this but can't find it. I'd appreciate any explanation you could give me.

Thanks

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emf= -ΔΦ/Δt, more accurately, the negative of the time derivative of the flux. The magnitude of the emf is maximum when the flux-time graph is steepest. ΔΦ is the change of the flux in time interval Δt.
As the graph consists of linear segments, the emf is constant within one segment. The vertical lines do not mean anything.
ehild
 
Actually there's no maximum or minimum value. Just polarity change due to changes in gradient.Normally verticall line is dotted.
 
Thanks heaps for this.
 

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