Free Electromagnetic Induction MCQs with Answers
22 Electromagnetic Induction MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
22 questions · page 3 of 3
21. In an ideal transformer, if the primary voltage is doubled and the turns ratio remains the same, what happens to the secondary current?
- A. Doubles
- B. Halves
- C. Remains the same
- D. Becomes four times
Explanation: With the turns ratio fixed, doubling the primary voltage doubles the secondary voltage, and for a given load resistance the secondary current rises in proportion by Ohm's law. The power drawn from the primary rises fourfold to match. The halving answer would apply to comparing primary with secondary current at a fixed input, which is a different question.
Correct answer: Doubles22. A loop moves toward a stationary magnet. The induced current will:
- A. Enhance the motion
- B. Try to stop the approach
- C. Become zero
- D. Become alternating
Explanation: By Lenz's law the induced current sets up a field that opposes the change producing it, so the loop is repelled and work must be done to keep pushing it towards the magnet. That work is the source of the electrical energy generated, which makes Lenz's law a statement of energy conservation. A current that enhanced the motion would create energy from nothing.
Correct answer: Try to stop the approach