A straight horizontal wire of mass 10 mg and length 1 m carries a current of 2 ampere .What minimum magnetic field B should be applied in the region so that the magnetic force on the wire may balance its weight.
Answer & explanation
Correct answer: option 3
$\text{For weight to be balanced by magnetic force mg = ilB}$
$\Rightarrow B = \frac{mg}{iL}= 4.9 \times 10^{-5} T$