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.

A long straight horizontal wire is carrying a current I. At an instant, an alpha particle at a distance r from it, is travelling with speed v parallel to the wire in a direction opposite to the current. Find the magnitude and direction of the force experienced by the particle at this instant.

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.

A beam of electrons moving horizontally with a velocity of 3 × 10⁷ m/s enters a region between two plates as shown in the figure. A suitable potential difference is applied across the plates such that the electron beam just strikes the edge of the lower plate.