The iron lings represent the magnetic eld present at the instant you stopped the magnet The direction of the magnetic eld is along the direction of the iron lings Does the magnetic eld intercept the area of the circular wire Week 1 Day 1 Concept Question Loop in Uniform Field Correct answer 1 While a rectangular wire loop is pulled upward through a uniform magnetic eld B eld penetrating its bottom half as shown there is a current in the loop Electric Current Flow of Charge Electric Current I Charge Q owing across area A at time t Electric currents can also cause magnetism Current and Magnetic Field Magnetic Field of Bar Magnet Current produces a magnetic eld as shown A magnet has two poles North and South Magnetic eld lines leave from the North end and go to the south end Visualizing the Magnetic Field Iron Filings Magnetic Flux Through Wire Loop Flux is the Generalization of Flow Product of perpendicular component of magnetic eld and area Electromotive Force Imagine a charge q moving around a closed path under the action of a force F Then the work done per unit charge is called the electromotive force Has the same dimensions as the electric potential so SI unit is the volt If the closed path is a circuit with resistance R then the electromotive force will cause a current to ow according to Loop is at rest and magnet is moving resulting in a changing magnetic ux through the loop and an induced emf and current in the loop Generalization Faraday s Law For a Closed Conduction Path Concept Question Loop In Uniform Field Induced current is source of induced magnetic ux that opposes the change in magnetic ux that caused it Correct answer While a rectangular wire loop is pulled sideways through a uniform magnetic eld B eld penetrating its bottom half as shown there is no current in the loop Lenz s Law Direction of Induced Current Induced EMF is in the direction that opposes the change in ux that caused it STOPPED HERE IN CLASS Concept Question Faraday s Law Loop Correct answer 1 A coil is falling downward directly beneath a magnet with its north pole pointing upward The current in the coil is counterclockwise and the force on the coil is up Conclusion Faraday s Law of Induction Changing magnetic ux generates electromotive force that opposes that change in ux
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