hw13 - Physics 21 Fall, 2004 Solution to HW-13 28 P 18 Two...

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Physics 21 Fall, 2004 Solution to HW-13 28 P18 Two long parallel wires 7.0 cm apart carry 16.5 A currents in the same direction. Determine the magnetic feld strength at a point P 12.0 cm From one wire and 13.0 cm From the other. αβ α α π/2 − α B B 1 β β π/2 − β B 2 The feld B at the point P will be the vector sum oF the felds From the two wires. We must fnd the components oF the two felds so we can add them. We can use the Law oF Cosines to solve For the angles α : 13 2 =12 2 +7 2 2(12)(7) cos α α =81 . 79 12 2 =13 2 2 2(13)(7) cos β β =66 . 01 The magnitude oF the felds are obtained From B = µ 0 I/ 2 πR , where R 1 =0 . 012 m For the leFt wire and R 2 . 013 m For the right wire. The diagrams show how we can use geometry to fnd the components oF B 1 and B 2 : B 1 = µ 0 I 2 π (0 . 12 m) ³ cos( π/ 2 α ) ˆ i +sin( 2 α ) ˆ j ´ B 2 = µ 0 I 2 π (0 . 13 m) ³ cos( 2 β ) ˆ i sin( 2 β ) ˆ j ´ Subsituting the numbers, we fnd B = B 1 + B 2 =( 5 . 04 ˆ i 0 . 64 ˆ j ) × 10 5 T 28 P32 A small loop oF wire oF radius 1.8 cm is placed at
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This note was uploaded on 08/06/2008 for the course PHYS 21 taught by Professor Hickman during the Fall '07 term at Lehigh University .

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