A straight wire AB of mass 40g and length 50cm is suspended by a...

The formula to calculate the magnetic force on the conductor is given by

${F}_{B} = ILB . . . \left(1\right)$

The formula to calculate the gravitational force on the conductor is given by

${F}_{G} = mg . . . \left(2\right)$

Equate both the equations and simplify to obtain the required current through the conductor.

$\begin{cases}ILB & = & mg \\ & ⇒ & I = \dfrac{mg}{LB} . . . \left(3\right)\end{cases}$

Substitute the values of the known parameters into equation (3) to calculate the required current through the conductor.

$\begin{cases}I & = & \dfrac{\dfrac{40}{1000}kg \times 10m{s}^{- 2}}{0 . 5m \times 0 . 40T} \\ & = & 2A\end{cases}$