Examples of Lenz's Law

# Examples of Lenz's Law - left loop • The switch had been...

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Physics 202 Thursday, April 8, 1999 Announcements: Lab quiz next week on Lab # 8 (RC circuits) Lecture notes: Examples of Lenz's Law Current in the loop is such that it creates a B field opposite to the motion of the magnet o If the magnet moves towards the loop, the current in the loop is clockwise; o If the magnet is moving away, the current is counerclockwise. The setup is exactly oppositeas the previous example o If the magnet is moving towards the loop, current is counterclockwise.

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o If the magnet is moving away, current is clockwise. At t= 0 the switch is closed; Current in the left hand loop (counterclockwise) gives rise to a magnetic field, that points to the left and increases with time. o With time, the induced current in the right hand loop must be in a direction that produces an induced magnetic field that opposes the magnetic field due to the left hand loop. o The direction of current in the right loop is opposite that of the
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Unformatted text preview: left loop. • The switch had been closed for a long time and at t= 0 it was opened. The magnetic field still points to the left, but it is decreasing with time. o The induced current in the right loop is such that it must produce a magnetic field that opposes the change in the magnetic field due to the left loop. o The induced current in the left loop is the same as the current in the right loop. Both are counterclockwise. See also problem 31-5 on page 777 of the text for an additional example Applications of Faraday's Law • Generators: Area changes with time, but magnetic field stays constant o Φ B = B (dot product) A = BAcos θ o If the coil is being rotated, Φ B = BAcos ϖ t ξ = - d Φ B /dt = + BA ϖ cos ϖ t o If there are N turns; €€€€€€€€€ξ = +N BA ϖ cos ϖ t Several in class demonstrations were performed to demonstrate Lenz's Law and Faraday's Law...
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Examples of Lenz's Law - left loop • The switch had been...

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