Can a transformer be used to convert direct current? Why?

A transformer is an electrical device used to change voltage. It basically consists of an iron core, a primary coil and at least one secondary coil. Transformers use the principle of electromagnetic induction to transfer electrical energy from one circuit to another without changing the frequency of the current.

However, transformers cannot be used to convert direct current because electromagnetic induction can only occur in alternating current. The direction of DC current is constant, so it cannot produce changes in the magnetic field, and thus cannot produce electromagnetic induction.

If a transformer is used to convert DC power, the end result is that the expected voltage conversion and power conversion cannot be achieved. This is because a transformer requires alternating current to produce a changing magnetic field, while direct current cannot produce a changing magnetic field. Therefore, in a transformer, the magnetic field does not change and the secondary coil does not sense electromagnetic energy from the primary coil.

Likewise, transformers rely on electromagnetic induction to change voltage because the voltage and current amplitudes of alternating current are constantly changing. In a transformer, voltage can be increased or decreased by using the proportional relationship between the primary and secondary coils. This proportional relationship is achieved through the turns ratio of the transformer, that is, the ratio of coil turns in the primary coil and secondary coil. If you put DC into a transformer, the transformer will not be able to change the voltage because the turns ratio is monotonic.

In short, transformers cannot be used to convert direct current, but can only be used to convert the voltage and power of alternating current. For DC voltage and power conversion, other electrical equipment such as DC voltage stabilizers and DC transformers can be used. Therefore, for DC systems, we need to use specially designed equipment to achieve voltage and power conversion.