Question

Can a transformer step up or step down dc power supply?

Hint:

Remember: Transformers need "motion" to work—not physical motion, but the "motion" of an alternating current changing direction 50 or 60 times a second. DC is "static," so the transformer remains "silent."

Answer 1

Step 1: Core Answer.
No, a transformer cannot step up or step down a DC (direct current) power supply. Transformers are designed specifically to operate with AC (alternating current) systems.

Step 2: Underlying Principle.
The working of a transformer is based on the principle of Faraday’s Law of Electromagnetic Induction. This requires a continuously changing magnetic flux to induce an electromotive force (EMF) in the secondary winding. $$e = -N \frac{d\Phi}{dt}$$ In a DC circuit, the current is constant, which means the magnetic field produced is stationary and the change in flux ($\frac{d\Phi}{dt}$) is zero.

Step 3: Consequence of Using DC.
If a constant DC voltage is applied to the primary coil of a transformer:

No EMF will be induced in the secondary coil because there is no change in magnetic flux.
Since there is no back EMF to oppose the input voltage, the primary coil will draw a very high current, which can lead to overheating and potentially burning out the transformer windings.