Question

Assertion (A) : An electron and a proton enter with the same momentum p in a magnetic field B such that p ⊥ B. Then both describe a circular path of the same radius. Reason (R) : The radius of the circular path described by the charged particle (charge q, mass m) moving in the magnetic field B is given by r = mv/qB.

Assertion (A) : The energy of a charged particle moving in a magnetic field does not change. Reason (R) : It is because the work done by the magnetic force on the charge moving in a magnetic field is zero.

Derive an expression for magnetic force F acting on a straight conductor of length L carrying current I in an external magnetic field B. Is it valid when the conductor is in zig-zag form ? Justify.

A straight wire of length 1.0 m is placed along x-axis, in a region with magnetic field B = (3î + 2ĵ) T. A current of 2.0 A flows in the wire along +x direction. The magnetic force acting on the wire is :