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Magnetic Field — Physics STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 SciencePhysicsMagnetic Field3 Marks
Question
A straight horizontal wire of mass 10mg and length 1.0m carries a current of 2.0A. What minimum magnetic field B should be applied in the region, so that the magnetic force on the wire may balance its weight?
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Answer

Mass $=10\text{mg}=10^{-5}\text{kg}$ Lenght $=1\text{m}$$\text{I}=2\text{A}$
Now, $\text{Mg}=\text{ilB}$$\Rightarrow\text{B}=\frac{\text{mg}}{\text{il}}=\frac{10^{-5}\times9.8}{2\times1}$
$=4.9\times10^{-5}\text{T}$

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