Single Choice

A long straight wire carries a current of $$\pi\ amp$$. The magnetic field due to it will be $$5\times 10^{-5}\ weber/m^2$$ at what distance from the wire $$[ \mu_0=$$ permeability of air ]

A$$10^4\mu_0$$ metre
Correct Answer
B$$\dfrac{10^4}{\mu_0}$$ metre
C$$10^6\mu_0$$ metre
D$$\dfrac{10^6}{\mu_0}$$ metre

Solution

B=
μ0
2π

i
r

⇒5×10−5=
μ0
2π

×
π
r

⇒r=104 μ0 metre

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