An Electromagnetic Field Exists Only When There Is

Answer: D. Current

An electromagnetic field exists only when there is current.

Solution

Christian Oersted has discovered that whenever current flows through a conductor there will be a magnetic field. This magnetic field can be detected by placing a compass near the conductor. This phenomenon can be observed with the DC as well as AC.

So, an electromagnetic field exists only when there is current. Option D is the correct answer.

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