WAEC Physics 2025 Objective — Question 46
Question 46 of 51 from the West African Examinations Council (WAEC) Physics 2025 Objective paper, with the correct answer and a full explanation.
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An electron moving with a speed of 5.0×10⁵ ms⁻¹ enters a uniform magnetic field at 90°. Calculate the magnitude of the magnetic force on the electron if the magnetic field intensity is 0.25T. [e = 1.6×10⁻¹⁹C]
- A. 1.0×10⁻¹⁴N
- B. 2.0×10⁻¹⁴NCorrect
- C. 3.0×10⁻¹⁴N
- D. 4.0×10⁻¹⁴N
Explanation
F = qvB sinθ; sin90° = 1. F = 1.6×10⁻¹⁹×5×10⁵×0.25 = 2.0×10⁻¹⁴N.
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