Magnetic fields are produced by
A) constant electric currents.
B) electric currents that vary sinusoidally with time.
C) time-varying electric fields.
D) all of the above.
E) only (a) and (b) above.

Question

Quizplus · Accepted Answer

Magnetic fields can be produced by constant electric currents, as shown by Ampere's law, and also by electric currents that vary sinusoidally with time, as in an electromagnet. Additionally, time-varying electric fields can produce magnetic fields according to Faraday's law. Therefore, all of the above choices are correct.

Magnetic Fields Are Produced by