In a velocity selector, crossed electric and magnetic fields of 3.0 × 10⁴ V/m and 0.20 T act on a beam of ions. At what speed do ions pass through undeflected?
Correct answer A. 1.5 × 10⁵ m/s
Explanation
An ion is undeflected when the electric and magnetic forces balance: qE = qvB, so v = E/B = 3.0 × 10⁴ ÷ 0.20 = 1.5 × 10⁵ m/s, independent of charge and mass.
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