Unformatted text preview: 1. (a) The magnitude of the magnetic ﬁeld due to the current in the wire, at a point a distance r from
the wire, is given by
With r = 20 ft = 6.10 m, we ﬁnd
B= (4π × 10−7 T · m/A)(100 A)
= 3.3 × 10−6 T = 3.3 µT .
2π (6.10 m) (b) This is about one-sixth the magnitude of the Earth’s ﬁeld. It will aﬀect the compass reading. ...
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