Problem 20.69 You have 15 m of wire, which you want to use to construct a 42 cm

Question

Problem 20.69

You have 15 m of wire, which you want to use to construct a 42 cm diameter coil whose magnetic field at its center will exactly cancel the earth’s field of 0.55 gauss.

Part A

What current will your coil require?

Express your answer to two significant figures and include the appropriate units.

A

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Problem 20.69

You have 15 m of wire, which you want to use to construct a 42 cm diameter coil whose magnetic field at its center will exactly cancel the earth’s field of 0.55 gauss.

Part A

What current will your coil require?

Express your answer to two significant figures and include the appropriate units.

A

SubmitMy AnswersGive Up

Explanation / Answer

magnetic field for circular coil,

B = u0 I N /2r

5.5 x 10^-5 T = (4pi x 10^-7) x I x N / (0.42 m)

N I = 18.38

N = no of turns and I = current in coil

and total length = 2pi R * N

2pi * 0.21 * N = 15

N = 11.37

so 11.37 x I = 18.38

I = 1.62 A

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