CAPF AC 2020 Q2: Science & Technology – Physics
- (a) never intersect
- (b) can originate from same point
- (c) can terminate at same point
- (d) can intersect depending on situation
Answer: (a) never intersect
Explanation
Magnetic field lines never intersect
How to think: a field line shows one direction at each point.
So ask: can one point have two directions?
It cannot.
A magnetic field line shows the direction of the magnetic field at each point.
If two lines crossed, the field would have two directions at one point.
A compass needle there would have to point two ways at once, which is impossible.
| Property of magnetic field lines | Detail |
|---|---|
| Shape | Closed, continuous loops |
| Direction outside the magnet | North pole to south pole |
| Direction inside the magnet | South pole to north pole |
| Crowding | Closer lines mean a stronger field |
| Intersection | Never |
The options checked:
| Option | Verdict |
|---|---|
| (a) never intersect | Correct |
| (b) can originate from same point | Incorrect; two lines from one point would give two directions there |
| (c) can terminate at same point | Incorrect; the lines are closed loops and do not end |
| (d) can intersect depending on situation | Incorrect; there is no such situation |
Answer: (a) never intersect.
Why each option is right or wrong
- (a) CORRECT. Crossing lines would mean two field directions at one point, which cannot happen.
- (b) Incorrect. Two lines that originate from the same point would give two directions at that point.
- (c) Incorrect. Magnetic field lines are closed loops; they do not terminate anywhere.
- (d) Incorrect. The rule has no exceptions; field lines of one source never intersect.
Key point
Magnetic field lines: closed loops, north to south outside the magnet, south to north inside, closer where the field is stronger, and they never intersect.
Remember
Magnetic field lines are closed loops that never cross.
Common mistakes
- Thinking field lines start at the north pole and end at the south pole; they continue inside the magnet.
- Believing lines can cross near the poles because they look crowded there.
- Confusing them with electric field lines, which do start and end on charges.
Exam tip
Educated guess: (a) and (d) are opposites, so one of them is the answer. One point, one direction settles it for (a).
Sources
- NCERT Class X Science — Magnetic Effects of Electric Current
- NCERT Class XII Physics — Magnetism and Matter