JAMB Physics 2024 Paper

Concept:The ion moves through crossed electric and magnetic fields without deflection. Its velocity is determined by equating the electric force and the magnetic force.Explanation:The electric force acting on the ion is $F_E = qE$. The magnetic force acting on the ion is $F_B = qvB$. For the ion to pass straight through, the net force must be zero. Thus, $qE = qvB$. Cancel the charge $q$ on both sides of the equation. This gives $v = \dfrac{E}{B}$. This is the velocity at which the ion emerges without being deflected.Answer:The resultant emergent velocity is $\dfrac{E}{B}$. Therefore, the correct option is A.