Question

When an iron bar is moved over a bar magnet along its length the attractive force

• A. increases first and then decreases
• B. decreases first and then increases
• C. remains same
• D. increase

Answer 1

The correct option is B

decreases first and then increases

1. We know that the force of attraction depends on a number of magnetic field lines.
2. At poles, field lines are close to each other which means the force of attraction is strong at poles.
3. As we move to the center of the magnet the magnetic field becomes small and hence, we experience less force at center.
4. Therefore, When an iron bar is moved over a bar magnet along its length the attractive force decreases first and then increases.

Hence, When an iron bar is moved over a bar magnet along its length the attractive force decreases first and then increases.

Therefore, the correct option is option (B).