Q1. [1] medium thorough-understanding
Which of the following best explains why one end of a current-carrying solenoid behaves as a north pole and the other as a south pole?
(A) The copper wire conducts current better at one end than the other, creating an asymmetry.
(B) The direction of current flow as seen from each end of the solenoid is opposite (clockwise at one end, anticlockwise at the other), producing opposite magnetic poles.
(C) The combined magnetic fields of all the turns reinforce each other along the axis, producing a net field that exits from one end and enters the other, just as in a bar magnet.
(D) The solenoid develops poles only when a soft-iron core is inserted inside it.
- A The insulation on the copper wire creates a charge separation at each end.
- B Current flows in opposite directions at the two ends of the solenoid, creating opposite poles.
- C The combined magnetic fields of all the turns reinforce each other, producing a net field that exits from one end and enters the other, just as in a bar magnet.
- D The solenoid develops poles only when a magnetic material is placed inside it.
Generated by claude-sonnet-4-6 · 2026-06-26 01:12 · grounding rag
Model Answer
Answer: (C)
The combined magnetic fields of all the turns reinforce each other, producing a net field that exits from one end and enters the other, just as in a bar magnet.
Source: Magnetic Field due to a Current in a Solenoid, Chapter 12
Explanation
- Option C is correct because the textbook explicitly states that the field pattern of a current-carrying solenoid is similar to that of a bar magnet, with one end acting as north pole and the other as south pole due to the reinforcement of fields of all turns along the axis.
- Option B is partially true (current direction does appear opposite at each end) but it is not the complete or best explanation — the textbook emphasises field reinforcement and the bar magnet analogy, not asymmetry in current direction.
- Option D is wrong: poles form even without a magnetic core; the soft-iron core only strengthens the field (electromagnet).
- For MCQs, pick the option that most completely matches the textbook explanation.