Class l Help Assignment 5 Begin Date: 3/24 2018 12:00:00 AM Due Date: 414 2018 1
ID: 2040689 • Letter: C
Question
Class l Help Assignment 5 Begin Date: 3/24 2018 12:00:00 AM Due Date: 414 2018 11:59:00 PM End Date: 4 16 2018 11:59:00 PM (6%) Proble 3: An MRI technician moves his hand from a region of very low magnetic field strength into an MRI scanner's 2.00?field with his fingers pointing in the drection of the field. His wedding ring has diameter of 2.45 cm and it takes 0.25 s to move it into the ficld. Randomized Variables d-2.45 cm t0.25 s 33% Part (a) what average current is induced in the ring in A if its resistance is 0.0100 12? Grade Summary 00% 100% Potential sin cos0 cotan asnacost cosh tanh cotanl Atteupts remsiting. 3 (1% per allenp) detailed view O Degrees O Radians I give up! reedback: 06 deduui per eedk Submission listory AnSwer Hints Feedback Totals Totals 0% 046 096 | 0% là 33% Part (b) what average power is dissipated in mw? ? 33% Parl (c) Whal Iragielic field is induced t lhe center ofthe ritig in T?Explanation / Answer
a)
magnetic flux = B*A
A = area of cross section of ring = pi*r^2
r = radius = 2.45/2 = 1.225 cm = 1.225*10^-2 m
induced emf = rate of change in flux
emf = (dB/dt)*A = (B2-B1)*pi*r^2/t
emf e = (2-0)*pi*(1.225*10^-2)^2/0.25 = 3.77*10^-3 V
average current i = e/R = 0.377 A <<<---------ANSWER
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average power = i^2*R = 1.42 mW
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(c)
magnetic field B = uo*i/(2*r)
B = 4*pi*10^-7*0.377/(2*1.225*10^-2)
B = 1.934*10^-5 T