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People say that negative sign has something to do with Lenz's law. I understood that negative sign is used to get correct sign of emf according to definition of emf. But how we can relate negative sign with Lenz's law definition? If there is any relation Lenz law then how do you come to know that with only a negative sign?

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If you would recall, Lenz's law states that the induced current produced in a circuit always flows in such a direction that it opposes the change or cause that produced it. It's similar to inertia. Now, consider a magnet moving towards a conducting loop along the axis of the loop. Since the magnet is moving closer, the magnetic field experienced by the loop is stronger, and so, the flux passing through the loop is increasing. This would cause the induction of a current in the loop that opposes the increase in flux - hence the expression $-\frac{\mathrm{d}\Phi}{\mathrm{d}t}$

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  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – Chris May 29 at 9:37
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In the Maxwell Equations in differential-form, the sign of Faraday's Law must have that negative sign, or else the electric and magnetic fields won’t satisfy the wave equation.

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