Magnetic Effects of Electric CurrentPractice Questions & MCQs

Q1. In Fleming's left-hand rule, which finger points in the direction of the magnetic field?

• A.The forefinger (first finger)
• B.The middle finger
• C.The thumb
• D.The little finger

Answer: A. The forefinger (first finger)

Q2. Consider the following statements about electromagnetic induction: (I) A changing magnetic flux induces a current. (II) Faraday discovered electromagnetic induction. (III) A steady magnetic field induces a large current. Which of the above statement(s) is/are correct?

• A.None of these
• B.Only I and II
• C.Only I
• D.Only III

Answer: B. Only I and II

NCERT fact (physics, chapter 'Magnetic Effects of Electric Current'): Correct: I, II. Why option B fits - Correct. Distractor analysis: option A) 'None of these' is wrong because Re-check each statement individually; option C) 'Only I' is incorrect: Re-check each statement individually. Final answer - B) Only I and II.

Q3. An AC generator's coil rotates at 50 rev/s. Doubling the rotation speed doubles which of the following?

• A.Both the peak EMF and the frequency
• B.Only the frequency
• C.Only the peak EMF
• D.Neither

Answer: A. Both the peak EMF and the frequency

Given 50, asked for the unknown. By EMF_peak = NABω, frequency f = ω/2π. EMF_peak = NABω, frequency f = ω/2π. Both scale linearly with ω, so doubling ω doubles both. Putting it together option A) Both the peak EMF and the frequency.