Question

Describe what happens to the electric field lines when two objects with unlike charges are brought near each other.

Answer 1

Key points first: field lines start on positive charges and end on negative charges; their density shows field strength; they never cross and show the direction a positive test charge would move.

What you see as two unlike charges are brought together
- Lines that originally left the positive object and ended on faraway negative regions (or at infinity) increasingly curve and join directly to the nearby negative object. In other words, more lines connect the + to the − as the separation decreases.
- The lines between the charges become denser and straighter (roughly directed from + to −), indicating a stronger electric field in the gap and a stronger attractive force.
- Away from the pair the pattern changes: for a closely spaced equal +q and −q you get the familiar dipole pattern (field concentrated between the charges and weaker far away). If the magnitudes differ, some excess lines still radiate to or from infinity, showing a net charge.
- Field lines never cross; they rearrange smoothly by superposition of the two fields as positions change.
- For conducting objects, charges redistribute on the surfaces so that lines meet the conductor surfaces at right angles; as they approach, surface charge concentrates on facing surfaces and the normal field between them strengthens.

Limiting case
- If the opposite charges are brought into contact they neutralize each other and the external field lines disappear (no net field remains).

Physical intuition: the pattern of lines “pulling” from + to − visually represents the attractive interaction — as the objects get closer the lines connecting them shorten, become more numerous per area, and the attractive force increases.