question_answer

A charged particle moves through a magnetic field in a direction perpendicular to it. Then the

A)  acceleration remains unchanged

B)  velocity remains unchanged

C)  speed of the particle remains unchanged

D)  direction   of  the  particle  remains unchanged

Correct Answer: C

Solution :

                 When a charged particle moves through a perpendicular magnetic field, then a magnetic force acts on it which changes the direction of particle but does not alter the magnitude of its velocity (ie, speed). Note: If a charged particle moves at\[45{}^\circ \]to magnetic field then path of the particle will be a helix whose circular part has radius as per the relation \[r=\frac{mv\sin \theta }{qB}\]