A straight horizontal wire of mass 10 mg and length 1.0 m carries a current of 2.0 A. What minimum magnetic field B should be applied in the region so that the magnetic force on the wire may balance its weight?


Given-



Mass of the wire, M = 10 mg = 10−5 Kg



Length of the wire, l = 1.0 m



Electric current flowing through wire, I = 2.0 A



It is said in the question, the weight of the wire should be balanced by the magnetic force acting on the wire.


Also angle between the length of the wire and magnetic field is


90°.


We k now weight of an object is given by



where,


m = mass


g = acceleration due to gravity =9.8 m/s2


We know,magnetic force acting on a current carrying wire in an uniform magnetic field is given by



where,


B= magnetic field


I = current


l = length of the wire


and θ = the angle between B and l


Thus,






1