Question 272: Magnetism and Matter

Question

A 2A current carrying straight metal wire of resistance $$1 \Omega$$, resistivity $$2 	imes 10^{-6} \Omega \mathrm{m}$$, 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 ________ $$	imes 10^{-1} \mathrm{~T}$$ (given, $$\mathrm{g}=10 \mathrm{~m} / \mathrm{s}^2$$).

Accepted Answer

$$\begin{aligned}
& i L B=m g 	ext { and } L=\frac{A R}{ho} \
& \begin{aligned}
	herefore B & =\frac{m g ho}{i A R} \
& =\frac{0.5 	imes 10 	imes 2 	imes 10^{-6}}{2 	imes 10 	imes 10^{-6} 	imes 1} \
& =0.5 \mathrm{~T}
\end{aligned}
\end{aligned}$$

Magnetism and Matter

Choose the correct answer: