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I have a question about the relationship between Faraday's and Lenz's law from a graph of the emf of Faraday's Law compared to the voltage in a coil. My question is whether or not this graph supports Lenz's law. Also, from this graph is it possible to determine if the direction of the induced current is going in the expected direction when the magnetic field is increasing? enter image description here

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  • $\begingroup$ How did you obtain this data? $\endgroup$ – BRT Apr 18 '17 at 22:52
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    $\begingroup$ Without a diagram showing the physical setup used to collect your data, your question probably cannot be answered. $\endgroup$ – David White Apr 19 '17 at 0:45
  • $\begingroup$ The data was obtained using a rigid pendulum with a coil at its end swings through a horseshoe magnet. A resistive load is connected across the coil and the induced voltage is recorded using a Voltage Sensor. Faraday's Law is used to estimate the magnetic field of the magnet from the maximum induced voltage. Also, the direction of the induced voltage as the coil enters and leaves the magnetic field is examined and analyzed using Lenz' Law. Is this sufficient information to answer the question? $\endgroup$ – Iwasykiw Apr 19 '17 at 1:05
  • $\begingroup$ This question does not make sense. If a resistor is in series with the coil, and $V$ is voltage across the resistor, then current is proportional to $V$ and EMF, given by $-LdI/dt$, should behave as derivative of $V(t)$. But there is is no trace of this in the graph, the EMF seems to copy the function $V(t)$. How did you determine EMF? $\endgroup$ – Ján Lalinský Jun 28 '18 at 8:34
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You could say something about Lenz law if you had measured the current too (positive or negative). You should measured EMF and current, then cross-plot it carefully because of the signs involved.

If you only calculated V and measured EMF you can't 'prove' Lenz's law because you've used it implicitly (the minus sign at Faraday's law from Maxwell's equations)

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