Induced Electric Field and Faraday's law

AI Thread Summary
The discussion revolves around a physics problem involving a cylindrical magnet producing a strong magnetic field and the calculation of the induced electric field using Faraday's law. The user has calculated the rate of change of the magnetic field (dB/dt) as 19.5 Tesla/second but is unsure about the application of the formula E = (r/2)(dB/dt) for the induced electric field. A suggestion is made to set up the magnetic field as a sinusoidal function and differentiate it with respect to time, incorporating the angular frequency (ω = 2π/T) into the calculations. The user is seeking clarification on where their calculations may have gone wrong. Accurate application of Faraday's law is crucial for determining the correct induced electric field.
DarkWarrior
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Hello, I'm stuck (again) on a physics problem.

The problem:

Early in 1981 the Francis Bitter National Magnet Laboratory at M.I.T. commenced operation of a 3.3 cm diameter cylindrical magnet, which produces a 30 T field, then the world's largest steady-state field. The field magnitude can be varied sinusoidally between the limits of 29.6 and 30.9 T at a frequency of 15 Hz. When this is done, what is the maximum value of the magnitude of the induced electric field at a radial distance of 1.6 cm from the axis?

What I've done so far: I've used Faraday's law, and after messing around with the equation I got E = (r/2)(dB/dt). As I understand it, the induced electric field is inside the magnetic field (r is less than R), so I thought this equation was correct.

R= .0165 m
r = .016 m
dB/dt = 19.5 Tesla/second. Since the frequency is 15, you multiply the difference of 30.9 and 29.6 by 15, getting 19.5

However when I plug the numbers in, my answer comes out wrong. Can someone point out where I screwed up? Thank you!
 
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DarkWarrior said:
Hello, I'm stuck (again) on a physics problem.

The problem:

Early in 1981 the Francis Bitter National Magnet Laboratory at M.I.T. commenced operation of a 3.3 cm diameter cylindrical magnet, which produces a 30 T field, then the world's largest steady-state field. The field magnitude can be varied sinusoidally between the limits of 29.6 and 30.9 T at a frequency of 15 Hz. When this is done, what is the maximum value of the magnitude of the induced electric field at a radial distance of 1.6 cm from the axis?

What I've done so far: I've used Faraday's law, and after messing around with the equation I got E = (r/2)(dB/dt). As I understand it, the induced electric field is inside the magnetic field (r is less than R), so I thought this equation was correct.

R= .0165 m
r = .016 m
dB/dt = 19.5 Tesla/second. Since the frequency is 15, you multiply the difference of 30.9 and 29.6 by 15, getting 19.5

However when I plug the numbers in, my answer comes out wrong. Can someone point out where I screwed up? Thank you!
Set up the equation for the field as a function of time (B = sinusoidal term + constant). Then differentiate with respect to time. There will be a factor \omega = 2\pi/T in the equation.

AM
 
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