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So electric fields are produced due to presence of charged particles and magnetic fields are produced due to motion of charged particles. In DC circuits, a current-carrying wire involves the motion of electrons, which are charged particles, so both magnetic and electric fields are produced. So why is it that only Alternating Current produces EM waves? Why do we need the changing magnetic fields? Similarly, is the motion of electrons around the atom’s nucleus what produces the continuous electromagnetic waves rather than only the transition between two energy levels that only does so?

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An EM wave is an oscillation of the EM fields- which requires them to vary in time. As you mentioned, DC produces a magnetic field, but a constant one.

For your second question, it is true that a classical orbiting-electron model would produce EM radiation, and it is one of the reasons that led to a quantum explanation: see the Bohr Model.

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  • $\begingroup$ If my second question is true about electrons continuously producing electromagnetic waves, doesn’t that violate the conservation of mass law considering that photons emitted do have a mass. $\endgroup$ Jul 7, 2020 at 20:15
  • $\begingroup$ The photons don't have mass, but they do carry energy. If you take the classical model, the electron should lose energy and fall to the center. This is one of the problems with the classical model. $\endgroup$
    – Rd Basha
    Jul 8, 2020 at 6:06
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    $\begingroup$ So its not real that it produces electromagnetic waves while orbiting but just by energy level transitions according to the quantum explanation? $\endgroup$ Jul 9, 2020 at 8:14

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