Answer: Iron.
- A Aluminium
- B Iron
- C Copper
- D Bismuth
Correct answer: B. Iron
Explanation: Iron (along with cobalt and nickel) is ferromagnetic, showing strong attraction to an external field and retaining magnetism once the field is removed.
Magnetic field lines form closed loops: outside the bar magnet they run from the N pole to the S pole; inside, they continue from S back to N, so the lines never start or end anywhere.
Concept context
Bar magnets, Earth's magnetism, and how different materials respond to an external magnetic field - diamagnetic, paramagnetic, and ferromagnetic behaviour.