Short Answer
Electromagnetic momentum flux through a surface is the best answer.
Electromagnetism questions become manageable once you separate source, field, potential, current, and force. Most wrong answers mix those layers together or ignore direction.
The Maxwell stress tensor Tᵢⱼ = ε₀(EᵢEⱼ − ½δᵢⱼE²) + (1/μ₀)(BᵢBⱼ − ½δᵢⱼB²) gives EM force per unit area on surfaces.
Why This Answer Is Correct
This is a Hard-level question in Electromagnetism. The prompt is really testing whether you can connect the concept to its defining physical relationship instead of picking a nearby-but-wrong term.
Keep charge, field, potential, and current distinct. That single habit fixes a large fraction of electromagnetism errors.
Choices At A Glance
- A. Thermal stress in crystals
- B. Electromagnetic momentum flux through a surface
- C. Electric potential between two plates
- D. Magnetic domain boundaries
When similar options appear on an exam, eliminate the ones that break the core law, use the wrong units, or confuse a definition with a consequence.
Topic Snapshot
Topic: Electromagnetism
Difficulty: Hard
Best next move: Re-state the governing law in your own words, then solve one more example from the same topic before moving on.