Transformers and DC: Can a conventional transformer step up or step down a DC voltage directly (without switching or chopping)? Choose the correct evaluation.

Introduction / Context:
Transformers rely on changing magnetic flux to induce voltage according to Faraday’s law. A steady DC produces no changing flux, so no secondary voltage is induced once transients die out. Understanding this limitation is critical in power conversion and explains why DC-DC converters first switch DC to AC-like waveforms before using a transformer.

Given Data / Assumptions:

• Conventional iron/ferrite-core transformer, not a special motor-generator or electronic converter.
• Input is steady DC, not a pulsed or switched waveform.
• No internal electronics present in the transformer itself.

Concept / Approach:
Induced voltage e = -N * dΦ/dt. With constant DC and a static core, dΦ/dt = 0 after initial transient, so e_secondary ≈ 0. Applying DC continuously risks saturating the core and overheating windings due to magnetizing current, offering no useful voltage transformation in steady state.

Step-by-Step Solution:

Verification / Alternative check:
DC-DC converters (e.g., flyback, forward) first chop DC into a pulsating waveform at kHz frequencies, then use a transformer; the presence of switching confirms the necessity of changing flux for induction.

Why Other Options Are Wrong:

• Works for DC / more turns / laminated cores / wire gauge: None overcome the need for time-varying flux. Turns ratio matters only with AC or changing waveforms.

Common Pitfalls:
Assuming “more turns” guarantees step-up without considering Faraday’s law; forgetting core saturation and heating when DC is applied directly.

Final Answer:
Incorrect — conventional transformers do not transform steady DC