A round coil of radius 6.75 cm and with 100 turns sits in a region of uniform ma

Question

A round coil of radius 6.75 cm and with 100 turns sits in a region of uniform magnetic field of strength.100 T directed into the page. The field is perpendicular to the plane of the coil, a) Sketch the situation. The field is turned off at a steady rate over a time interval of 5.0 s and then remains off. (fyi, this would be called ramping the field) During this 5.0 s time interval, the field is given by B(t) =.100(5.0 -1) (assume SI units). Explain why there is an induced EMF while the field is being ramped off? c) Find the magnitude of the EMF while the field is being ramped off. d) Indicate the direction of the induced current on your sketch. Explain why the current is in this direction.

Explanation / Answer

magnetic field is indicated by (X into sign) on paper. Coil with hundred turns is placed on paper.

(b) According to faradays law of induction we have rate of change of flux = induced emf in the oppositedirection

So flux through coil = .1 * (5 - t) * 100 * pi * (0.0675)^2

Now rate of change = - (0.1) * 100 * pi * (0.0675)^2

So EMF induced in opposite direction. = (0.1) * 100 * pi * (0.0675)^2

The direction of current is told using a simple method. If flux is decreasing current in coil flows to increase or maintain the flux or vice versa.

So here flux is decreasing . So current should flowin order to maintain the flux into the paper.

SO by right hand thumb rulecurrent flows clock wise in the coil.

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