Question

The magnetic field at the center of a 0.70-cm-diameter loop is 2.9 mT .

Part A

What is the current in the loop?

Express your answer in amperes.

Part B

A long straight wire carries the same current you found in part a. At what distance from the wire is the magnetic field 2.9 mT ?

Express your answer in meters.

Answer 1

Part A

magnetic field at the center of a loop is given by,

B = o*I/(2*r)

given, B = 2.9 mT = 2.9*10^-3 T

r = diameter/2 = 0.70/2 cm = 0.35*10^-2 m

o = 4*pi*10^-7

So, I = current = (2.9*10^-3)*2*(0.35*10^-2)/(4*pi*10^-7)

I = 16.15 Amp

Part B

Since magnetic field due to a long current carrying wire is given by,

B = o*I/(2*pi*d)

here, d = distance from wire = ??

B = 2.9 mT

So, d = (4*pi*10^-7)*16.15/(2*pi*2.9*10^-3)

d = 1.11*10^-3 m

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