Which quantity is increased in a step down transformer?

The correct answer is Option (2) → Current

A step-down transformer has fewer turns in the secondary than in the primary, so the secondary voltage is lower.

    \( \displaystyle \frac{V_s}{V_p} = \frac{N_s}{N_p} \lt 1 \)

For an ideal transformer the power is conserved:

    \( \displaystyle V_p I_p = V_s I_s \;\Rightarrow\; \frac{I_s}{I_p} = \frac{V_p}{V_s} = \frac{N_p}{N_s} \gt 1 \)

So the voltage is stepped down and the current is stepped up.

Option (1) Power — Incorrect. The output power at most equals the input power; a transformer cannot increase power.

Option (2) Current — Correct. The secondary current is larger than the primary current by the factor \( N_p/N_s \).

Option (3) Frequency — Incorrect. The induced emf has the same frequency as the input; a transformer does not change the frequency.

Option (4) Voltage — Incorrect. The voltage is decreased in a step-down transformer.

NCERT (2026-27):
Transformers – “… If the secondary coil has less turns than the primary (\( N_s \lt N_p \)), we have a step-down transformer. In this case, \( V_s \lt V_p \) and \( I_s \gt I_p \). That is, the voltage is stepped down, or reduced, and the current is increased.”