Question

at what distance from a long straight wire carrying current of 12 A will the magnetic field be equal to 3×10(-5)Wb m-2

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Answer 1

Given,

B=3×10−⁵ Wb/m²

i=12A

The magnetic field at a distance r from the long current carrying straight wire is given by,

B = μ⁰i/2πr

3 × 10-⁵ = 4π × 10-⁷ × 12 / 2πr

r = 2 × 10-⁷ × 4 × 10⁵

r = 8 × 10-² m

Hence,

Distance = r = 8 × 10-² m

Answer 2

Given:

I= 12A

B= 3×10^(-5)

Need to find:

Distance of wire where we can find given magnetic field

Solution:

It's a long wire as it's length is not specified,  we can consider it to be infinitely long.

• B= μ°I/ 2πA

• B= 2μ°I/ 4πA

We know,

• μ°/ 4π = 10^(-7)

• 3×10^(-5)= 2 ×10^(-7) × 12/A

• A= 8×10^(-2) m