In a robotic gripper, a straight conductor of length 0.25 m forms one side of a rectangular coil inside a uniform magnetic field of 0.15 T. The side is always kept perpendicular to the field. The gripper must exert an upward magnetic force equal to the weight of a small iron rod of mass 120 g.
Answer the following using g=10ms−2.
(i) Derive an expression for the current I required to produce an upward force F on the conductor when it is perpendicular to the magnetic field.
(ii) Calculate the current needed to lift the 120 g iron rod with the given magnetic field.
(iii) The power supply available can provide only 5 A. Suggest ONE change in either the conductor length or the magnetic field strength that would allow the gripper to lift the rod, and support your suggestion with a suitable calculation.