Physics
Physics
Problem
Two identical bar magnets are placed coaxially with their north poles facing each other, leaving a small air gap between them. Predict qualitatively (i) the shape of the magnetic field lines in the gap and (ii) whether the magnetic field at the midpoint of the gap is relatively strong or weak. Give reason.Intuitive explanation
When two north poles repel each other, the magnetic field lines between them are forced to spread outward and curve away from the gap's center—they can't flow straight across like they would between opposite poles. This spreading means the field lines are less concentrated at the midpoint, so the field strength there is actually weaker than it would be in a single magnet's gap. The key insight is that field line density directly shows field strength, and repulsion causes that density to drop sharply in the middle.
Intuitive explanation
When two north poles repel each other, the magnetic field lines between them are forced to spread outward and curve away from the gap's center—they can't flow straight across like they would between opposite poles. This spreading means the field lines are less concentrated at the midpoint, so the field strength there is actually weaker than it would be in a single magnet's gap. The key insight is that field line density directly shows field strength, and repulsion causes that density to drop sharply in the middle.