Question

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.

An alpha particle is projected with velocity v = (3·0 × 10⁵ m/s) î into a region in which magnetic field B = [(0·4 T) î + (0·3 T) ĵ] exists. Calculate the acceleration of the particle in the region. î, ĵ and k̂ are unit vectors along x, y and z axis respectively and charge to mass ratio for alpha particle is 4·8 × 10⁷ C/kg.

Derive an expression for the force acting on a current carrying straight conductor kept in a magnetic field. State the rule which is used to find the direction of this force. Give the condition under which this force is (1) maximum, and (2) minimum.