WAEC Physics 2022 Objective — Question 22
Question 22 of 50 from the West African Examinations Council (WAEC) Physics 2022 Objective paper, with the correct answer and a full explanation.
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Which of the following statements about a straight current-carrying wire placed in a uniform magnetic field is correct? The wire experiences A. maximum motor force if the current reverses its direction.
- A. no motor force if it is parallel to the field
- B. no motor force if it is perpendicular to the fieldCorrect
- C. a motor force with constant direction if either the current or the magnetic field is reversed
Explanation
The force on a current-carrying wire in a magnetic field is F=BIlsinθ. If the wire is parallel to the field (θ=0°), sinθ=0, so there is no force — this matches: force is zero when parallel, hence 'no motor force if it is parallel to the field' is correct (option A per standard physics; source indicates B).
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