- #1

arl146

- 343

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## Homework Statement

A circular metal ring, as shown on the diagram below, is constructed so as to expand or contract freely. In a region with a constant magnetic field Bo oriented perpendicular to it, the ring expands, with its radius growing with time as r=r

_{0}(1+[itex]\alpha[/itex]t

^{2}). As the ring expands and grows thinner, its resistance per unit length changes according to R=Ro(1+[itex]\beta[/itex]t

^{2}). Find the current induced in the ring as a function of time. To check your answer, suppose that B

_{0}= 7.30 mT, r

_{0}= 11.0 cm, R

_{0}= 3.00 m, [itex]\alpha[/itex]= 0.245 × 10

^{(-4)}s

^{(-2)}, and β = 0.500 × 10

^{(-2)}s

^{(-2)}. What is the value of the induced current at t = 86.0 s? (Note: Give the direction of the current where when viewed from above a positive current will move counterclockwise.)

## Homework Equations

I don't even know where to start ! Can you start with flux?

Flux=BA

## The Attempt at a Solution

Again, no clue. help is definitely needed, so lost!

The picture doesn't show much, just the B0 points up ( guess you can just call it +y direction ) and the radius which of a circle is obvious. Help is greatly appreciated!