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### Magnetic field and brain cells Suppose a power li…

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Indian Institute of Technology Kharagpur
Problem 29

# A circular loop of radius 9.0 $\mathrm{cm}$ is placed perpendicular to a uniform $0.35-\mathrm{T} \vec{B}$ ficld. You collapse the loop into a long, thin shape in 0.10 s. What is the average induced emf while the loop is being reshaped? What assumptions did you make?

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## Video Transcript

Okay. In this case, we're dealing with the circular loop off radius R where area is given by by our square from there when you could have salute the area changes to zero. In this soup, there is a magnetic field going downward or perpendicular to the plane off the loop. And yes, we're trying to find out what is the PMF induced. If you collapse the loop in some time, Delta t equals 0.1 2nd The magnetic field Is it a 0.35 tests and the radius is even by nine centimeter. Nine centimeter are zero foreign 09 major. So remember that electric field is Shania in socks over change in time. In this particular case, taxis be dot a So be stays what it is. And then we have ah, changing area that is happening when you work will absolutely loop on. There is a change in time involved changing area. He's basically the initial area minus the final area, which is zero divided by desert e. So be, uh, Delta t oh, are be The idea is by your square delta t. So this will come out to be B 0.35 time and the area 0.9 squared. So that is 0.81 I won't. And you do the math now. I just want to write it down Really easy. 0.350 point bond. That will give me 3.5 times 3.14 times 0.81 fold. That would be zero foreign 087 a date. Voltage. Oh, are 88. Maybe the what?