Single correct · +4 / −1
Gauss's law for magnetism states that the net magnetic flux through any closed surface is:
- (a) μ₀ Q_(enc)
- (b) zero
- (c) B· A
- (d) constant
Answer and solution
Answer (b) zero
Solution
Physics sir · 3 steps
Magnetic field lines never start or stop anywhere, so whatever goes into a closed surface comes back out.
- No magnetic charge. Electric field lines begin on positive charges and end on negative ones. There is no isolated magnetic pole (monopole) for magnetic field lines to begin or end on, so they always form closed loops.
- In equals out. Take any closed surface. Every field line that enters it must also leave it. Lines going in count as negative flux and lines coming out count as positive flux, so the two always cancel.
∮ B⃗ · dA⃗ = 0
- So. The net magnetic flux through any closed surface is zero, which is option (b).
The idea to keep. Gauss's law for magnetism is the magnetic version of Gauss's law with no charge term, because magnetic monopoles do not exist. Closed surface means zero net magnetic flux, always.
Answer from the NTA final answer key. Solution by PrepWiser.