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Question
A long straight wire carries a current of 35 A. What is the magnitude of the field B at a point 20 cm from the wire?
Solution
Current in the wire, I = 35 A
Distance of a point from the wire, r = 20 cm = 0.2 m
Magnitude of the magnetic field at this point is given as:
B = `mu_0/(4pi)(2"I")/"r"`
Where,
`mu_0` = Permeability of free space
= 4π × 10–7 T m A–1
B = `(4pi xx 10^-7 xx 2 xx 35)/(4pi xx0 .2)`
= 3.5 × 10–5 T
Hence, the magnitude of the magnetic field at a point 20 cm from the wire is 3.5 × 10–5 T.
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