Charge particle in magnetic field
A point charge moving in uniform magnetic field experiences a force on . Behaviour of charge particle depends on the angle ‘θ ‘ between .
Case 1, if θ = 00 or 1800
When the charged particle moves parallel or anti parallel to field then no net force acts on it & its trajectory remains a straight line.
Case 2, If θ is other than 00, 1800 & 900
Charge particle moves in a helical path of radius , completes one circle in time & travels a distance in one time period in the direction of field called pitch & is given by,
Case 3, If θ is 900
Charge particle moves in a circle at uniform speed.
Radius of circular path is
KE of particle is constant. It completes a cycle in time at angular frequency .
As the force acting on the particle is only normal & no tangential force is available thus speed & hence KE also of the particle will remain unchanged. As the kinetic energy of the charged particle remains constant. Hence no work is done in moving a charge particle moving at right angles to the magnetic field. However due to change in direction & are variables in direction.