Answer: Ampere's law was inconsistent for a changing electric field (capacitor plates).
- A Ampere's law was inconsistent for a changing electric field (capacitor plates)
- B Ordinary conduction current was too small in magnitude to detect in standard practice
- C Magnetic monopoles had just been experimentally discovered under most conditions encountered
- D Electric current was found to flow freely through a vacuum gap as frequently observed in practice
Correct answer: A. Ampere's law was inconsistent for a changing electric field (capacitor plates)
Explanation: Maxwell noticed that Ampere's law gave contradictory results for the magnetic field around a charging capacitor. Adding displacement current I<sub>d</sub> = ε_0 dΦ_E/dt made the law consistent.
In an electromagnetic wave, the oscillating electric field (E) and magnetic field (B) are perpendicular to each other and to the direction the wave travels - a purely transverse wave that needs no medium, unlike sound.
Concept context
Maxwell's equations, EM spectrum, properties, and applications of each band.