Question

Why can't a transformer be used to step up dc voltage?

Answer 1

When a d.c voltage source is applied across the primary of the transformer,the current in the primary coil remains constant. Hence there is no change in the magnetic flux linked with the secondary. Therefore the voltage across the secondary coil is zero.Thus a transformer can't step up dc voltage.

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Answer 2

Explanation:

The d.c supply does not produce a changing magnetic flux in the primary and hence no emf is set up in the secondary of the transformer.