1) An electron and proton moving parallel to each other in the same direction with equal momentum enter into a uniform magnetic field which is at right angle to thier velocites trace their trajectories in the magnetic field.

As the charge particle enters perpendicular to the magnetic field, the force will act perpendicular to the velocity. Thus the particle starts moving in the circular path but along different direction. As force and displacement are perpendicular the work done will be zero and kinetic energy will not change. But as it moves in circular path direction of momentum will change but magnitude is unchanged. Also, the radius of the path followed by both will be different as radius is directly proportional to the mass of the charged particle. The direction of force on the electron and the proton can be determined by Fleming’s left hand rule. According to this rule, if the thumb, forefinger, and middle finger of the left hand are stretched such that they are mutually perpendicular to each other and the index finger and the middle finger are pointing towards the directions of magnetic field and current respectively, then the thumb will point in the direction of the force.