Homework Help: Physics help?

Posted by Nadine on Friday, March 30, 2012 at 5:54pm.

A circular loop in the plane of the paper lies in a 0.78 T magnetic field pointing into the paper.
If the loop's diameter changes from 17.8 cm to 6.4 cm in 0.22 s, what is the direction of the induced current?
What is the magnitude of the average induced emf?
If the coil resistance is 2.9 Ω, what is the average induced current?

Physics help? - drwls, Friday, March 30, 2012 at 9:09pm
The induced current will be in the dorection that increases the flux through the loop.

The magnitude of the induced emf is
d(Phi)/dt = B*dA/dt
= 0.78T*(pi/4)[(.178^2 -.064)^2]/0.22s
= 0.077 V

Divide by 2.9 ohms for the induced current.
Physics help? - Nadine, Saturday, March 31, 2012 at 9:27am
Thank you!

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