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Unformatted text preview: 3. (a) The ﬁeld due to the wire, at a point 8.0 cm from the wire, must be 39 µT and must be directed due
south. Since B = µ0 i/2πr,
2π (0.080 m)(39 × 10−6 T)
= 16 A .
4π × 10−7 T · m/A (b) The current must be from west to east to produce a ﬁeld which is directed southward at points
below it. ...
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