P30_078 - 78. By the right-hand rule, the magnetic field...

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Unformatted text preview: 78. By the right-hand rule, the magnetic field B1 (evaluated at a) produced by wire 1 (the wire at bottom left) is at φ = 150◦ (measured counterclockwise from the +x axis, in the xy plane), and the field produced by wire 2 (the wire at bottom right) is at φ = 210◦ . By symmetry (B1 = B2 ) we observe that only the x-components survive, yielding B1 + B2 = 2 µ0 i cos 150◦ ˆ = −3.46 × 10−5 ˆ T i i 2π where i = 10 A, = 0.10 m, and Eq. 30-6 has been used. To cancel this, wire b must carry current into ˆ the page (that is, the −k direction) of value ib = 3.46 × 10−5 where r = √ 2π r = 15 A µ0 3 /2 = 0.087 m and and Eq. 30-6 has again been used. ...
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