A magnetic field that is uniform in space, but whose magnitude changes with time at a constant rate, is directed along the x-axis. A conducting ring of diameter 7.0 cm and electrical resistance 1.5x10-3 Ω lies in the y-z plane. If the induced current in the ring is observed to be 2.0 A, what is the rate of change (in T/s) of the magnitude of the magnetic field?

0.24T/s

Explanation:

This problem can be solved if use the Lenz's Law, that is

       ( 1 )

but this emf is for the ring:

and we can replace this value in ( 1 )

where we have taken the area of a circle and a radius of 70cm=0.07m. dB/dt is the ratio of change of the magnetic field. Hence the answer is 0.24T/s

I hope this is useful for you

regards

that would be b i just took the test : )