A narrow beam of singly charged positive ions enters a region that contains a uniform…
PHYSICS · Multi-part · CBSE · Physics · Moving Charges and Magnetism · Moving Charges and Magnetism
Problem
A narrow beam of singly charged positive ions enters a region that contains a uniform electric field E and a uniform magnetic field B. The two fields are mutually perpendicular to each other and each is perpendicular to the initial velocity v of the ions. The ions travel through the region without any noticeable change in speed.
Answer the following questions in the sequence given.
(i) Explain why, for an ion that travels straight through the region, the electric and magnetic forces acting on it must be equal in magnitude and opposite in direction.
(ii) Starting from the expressions for the magnitudes of the electric and magnetic forces, obtain the condition that the speed v of such an ion must satisfy in terms of E and B.
(iii) If the same arrangement of fields is now used for electrons entering with the same initial velocity direction, state and justify the required direction of the electric field for the electrons to emerge undeflected.