Velocity Selector Condition — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Velocity Selector Condition This condition applies to a velocity selector where a charged particle moves undeflected due to the perfect cancellation of electric and magnetic forces. The electric force acting on a charge q is given by F E = qE . The magnetic force acting on a charge q moving with velocity v is given by F B = qvB (assuming v B ). For the particle to move undeflected, the net force must be zero: F net = 0 . Equating the forces: F E = F B qE = qvB . Solving for the required velocity: v = E B . q 0 B 0 E 0 Assuming the electric and magnetic forces are always perpendicular (this is required for the simple cancellation). Confusing the condition for zero net force with the calculation of maximum force. Forgetting that the velocity must be perpendicular to both E and B for the simple cancellation to hold.