Electromagnetic induction: motional emf for a conductor moving in a magnetic field + example.

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Using electromagnetic induction, we compute motional emf for a conductor moving in a magnetic field.

We start by arguing the direction of the induced voltage using Lorentz force, and we argue the same direction of induced voltage using induction (in fact, the Lorentz force version is the same thing we did to derive the Hall voltage!).

In our induction motional emf approach, we use a moving conductor to complete a circuit, and we see that the inward magnetic flux is increasing for the loop bounded by the conductor.

We allow a small time, delta-t, to elapse, and we calculate the change in flux for the loop during that time. Then, applying Faraday's law, we use the rate of change in flux to calculate the potential difference in terms of the speed of the conductor. We obtain the same formula as we did for the Hall voltage in terms of drift velocity!

Finally, we apply our new formula to the motional emf across an airplane's wings. The induced voltage across the wings is computed by plugging into the formula, and we obtain a result of about 0.2V.

[SarrouTube]

Very good example !!! Clear explanation!! You can say the direction of current is opposite the direction of electrons . This is for students your explanation is more accurate using Lentz law.