# hw15 - Physics 21 Fall, 2009 Solution to HW-15 28-30 (a)...

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Unformatted text preview: Physics 21 Fall, 2009 Solution to HW-15 28-30 (a) Calculate the magnetic field at point P due to the current in the semicircular section of wire shown in the figure. Hint : Does the current in the long, straight section of the wire produce any field at P ?) The Biot-Savart Law gives d B = µ 4 π Id l × ( r − r ) | r − r | 3 . where | r − r | = R , and the vector r − r points from the current point r on the loop at d l to the field point r at P . Note that d B has the same magnitude and direction (into the page) at every point on the circular loop. Therefore, we can just take half of the result for the full circular current loop given in class or in section 28.5 of the text. The result is B = µ I 4 R (into the page) . The straight segments do not contribute to the magnetic field at P . In that case, d l and | r − r | are parallel, so their cross product is zero. 28-32 A solid conductor with radius a is supported by in- sulating disks on the axis of a conducting tube with inner...
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## This note was uploaded on 11/06/2009 for the course PHYS 21 taught by Professor Hickman during the Spring '07 term at Lehigh University .

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hw15 - Physics 21 Fall, 2009 Solution to HW-15 28-30 (a)...

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