Answer:
The second option is correct. He discovered electromagnetism after seeing a compass needle deflected by a flowing electric current.
Step-by-step explanation:
Hans Oersted made a remarkable discovery regarding the interaction of electricity and magnetism. He observed a compass needle's deflection caused by an electric current. This experiment in 1820 established a fundamental connection between these two phenomena. The flowing electric current created a magnetic field around a wire, demonstrating the concept of electromagnetism. This groundbreaking finding paved the way for subsequent advancements in physics, such as electromagnetic induction and the formulation of the laws of electromagnetism by James Clerk Maxwell.
Breaking down each option:
- The first option is incorrect because it pertains to electromagnetic induction, a phenomenon where an electromotive force (EMF) is induced across a conductor in response to a changing magnetic field. This significant discovery was actually made by Michael Faraday.
- The second option is the correct choice as it accurately states that Hans Oersted discovered electromagnetism through the deflection of a compass needle.
- The third option is an incorrect option because it suggests that Hans Oersted discovered electromagnetic induction, which is not the case.
- The fourth option is also incorrect because it incorrectly suggests that there is no change in current while changing the magnetic field. This statement is inaccurate, and it is not attributed to Hans Oersted.