Previous Year Question

A mobile phone does not require the very high voltage supplied by the mains. The charger must reduce the high input voltage to a low voltage suitable for the mobile battery and charging circuit.

In a step-down transformer, the secondary coil has fewer turns than the primary coil—

According to the transformer relation—

Therefore, if , then—

Thus, the output voltage is lower than the input voltage. Such a transformer is called a Step-down Transformer. NCERT-based SATHEE material also mentions the use of step-down transformers in phone chargers and device adapters.

However, a mobile battery requires DC, so a charger also requires rectification and regulation in addition to voltage reduction. Among the options given in the examination, the correct answer based on the voltage-reduction function is Step-down Transformer.

Concept Clarification: Modern phone chargers generally use an SMPS (Switched-Mode Power Supply) architecture.