A $2 \mathrm{~A}$ current carrying straight metal wire of resistance $1 \Omega$, resistivity $2 \times 10^{-6} \Omega \mathrm{m}$, area of cross-section $10 \mathrm{~mm}^2$ and mass $500 \mathrm{~g}$ is suspended horizontally in mid air by applying a uniform magnetic field $\vec{B}$. The magnitude of $B$ is__________.$\times 10^{-1} \mathrm{~T}\left(\right.$ given, $\mathrm{g}=10 \mathrm{~m} / \mathrm{s}^2$ )
JEE MAIN 2024, Diffcult
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$\mathrm{R}=\frac{\rho \ell}{\mathrm{A}} \Rightarrow \frac{2 \times 10^{-6} \times \ell}{10^{-5}}=1 \Rightarrow \ell=5$
$\mathrm{mg}=\mathrm{Bi} \ell$
$\mathrm{B}=\frac{\mathrm{mg}}{\mathrm{i} \ell}=\frac{5}{2 \times 5}=0.5=5 \times 10^{-1} \text { Tesla }$
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