An elastic conducting material is stretched into a circular loop of 9.75 cm radius. It is placed with its plane perpendicular to a uniform 1.06 T magnetic field. When released, the radius of the loop starts to shrink at an instantaneous rate of 56.9 cm/s. What emf is induced in volts in the loop at that instant?

0.37 V

Explanation:

emf = dΦ/dt, where

Φ = BA, so then

emf = d(BA)/dt

Recall that A = πr², on substituting for that too we have

emf = d(Bπr²)/dt

Since B is a constant, when we differentiate, we have

emf = Bπ d(r²)/dt

emf = Bπ 2r.dr/dt, on rearranging

emf = 2πrB dr/dt,

Now we go ahead and substitute the values given from the question so that

emf = 2 * 3.142 * 0.0975 * 1.06 * 0.569

emf = 0.370 V

Therefore, the induced emf in volts is 0.37 V

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.