Question

A long straight wire carries a current of 35A. What is the magnitude of the field B at a point 20cm from the wire
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Answer 1

$\huge{\underline{\tt{\red{Given-}}}}$

• Current in the wire, I = 35 A
• Distance of a point from the wire, r = 20 cm = 0.2 m

Formula-

$\small\underline{\overline{\mid{\bold{\orange{B= \dfrac{\mu_o I}{2\pi r}}} \mid}}}$

$\huge{\underline{\sf{\blue{Solution-}}}}$

putting values in formula we get,

$B= \dfrac{4 \pi \times 10^-7 \times 2\times 35}{4\pi\times 0.2}$

$B= 3\times 10^-5 \ T$

Answer 2

Given ,

Current (I) = 35 A

Distance (r) = 20 cm or 0.2 m

We know that , the magnetic field due to an infinitely long straight wire at distance r from it is given by

$\boxed{ \sf{B = \frac{ μ_{o} I}{2\pi}} }$

Thus ,

$\sf \mapsto B = \frac{4\pi \times {(10)}^{ - 7} \times 35 \times 2}{4\pi \times 20 \times {(10)}^{ - 2} } \\ \\ \sf \mapsto B =35 \times {(10)}^{ - 6} \: \: Tesla$

Therefore , the magnitude of the magnetic field is 35 × (10)^{-6} T