Magnetic Effects & Magnetism

JEE Main level, numerical answer, medium

198 of 276

Question 198 of 276

A straight wire AB of mass 40g40g and length 50cm50cm is suspended by a pair of flexible leads in uniform magnetic field of magnitude 0.40T0.40T as shown in the figure. The magnitude of the current required in the wire to remove the tension in the supporting leads is _____ AA. (Take g=10ms−2)\left.g=10m{s}^{-2}\right).

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Answer: 2

The formula to calculate the magnetic force on the conductor is given by
FB=ILB...(1){F}_{B}=ILB...\left(1\right)
The formula to calculate the gravitational force on the conductor is given by

FG=mg...(2){F}_{G}=mg...\left(2\right)
Equate both the equations and simplify to obtain the required current through the conductor.

ILB=mg⇒I=mgLB...(3)\begin{matrix}ILB & = & mg \\ & \Rightarrow & I=\dfrac{mg}{LB}...\left(3\right)\end{matrix}
Substitute the values of the known parameters into equation (3) to calculate the required current through the conductor.

I=401000kg×10ms−20.5m×0.40T=2A\begin{matrix}I & = & \dfrac{\dfrac{40}{1000}kg\times 10m{s}^{-2}}{0.5m\times 0.40T} \\ & = & 2A\end{matrix}

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