Why transformers work only with AC and not with DC
The first thing to know here is the meaning of AC and DC.
AC means Alternating Current. That is the current changes direction
DC means Direct Current. That is unidirectional current or single direction.
With the understanding of this meanings, the main reason why a transformer works only with AC is because, the AC causes a changing magnetic field and hence a flux which in turn links the secondary winding and hence an induced emf and current can flow. Meanwhile DC, does not cause a changing magnetic field hence no induction into the secondary winding.
So this is a phenomenon of Faraday's law of electromagnetic induction
AC means Alternating Current. That is the current changes direction
DC means Direct Current. That is unidirectional current or single direction.
With the understanding of this meanings, the main reason why a transformer works only with AC is because, the AC causes a changing magnetic field and hence a flux which in turn links the secondary winding and hence an induced emf and current can flow. Meanwhile DC, does not cause a changing magnetic field hence no induction into the secondary winding.
So this is a phenomenon of Faraday's law of electromagnetic induction