A square loop of side a hangs from an insulating hanger of spring balance. The magnetic field of strength `B` occurs only at the lower edge. It carries a current `I` . Find the change in the reading of the spring balance if the direction of current is reversed.

Explanation

Initially `F_(1)=mg+laB(` down wards `)`
when the direction of current is reversed
`F_(2)=mg=IaB(` down wards `)impliesDeltaF=2IaB`