For a step-up transformer, the ratio of the number of turns in the secondary coil to that in the primary coil, \( N_s/N_p \), is
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → greater than one
In a transformer the voltages are in the ratio of the numbers of turns, \( V_s/V_p=N_s/N_p \). A step-up transformer raises the voltage, \( V_s\gt V_p \).
Option (1) one — Incorrect. With \( N_s=N_p \) the output voltage equals the input voltage, so nothing is stepped up.
Option (2) greater than one — Correct. \( V_s\gt V_p \) needs \( N_s\gt N_p \), that is, the secondary has more turns than the primary and \( N_s/N_p\gt1 \).
Option (3) less than one — Incorrect. Fewer turns in the secondary give \( V_s\lt V_p \), which is a step-down transformer.
Option (4) greater or less than one, depending on the load — Incorrect. The turns ratio is fixed by the windings of the coils. The load changes only the currents drawn. The number of turns stays the same.
NCERT (2026-27):
Transformers – “Now, we can see how a transformer affects the voltage and current. We have:
\( \displaystyle V_s=\left(\frac{N_s}{N_p}\right)V_p \quad\text{and}\quad I_s=\left(\frac{N_p}{N_s}\right)I_p \qquad (7.36) \)
That is, if the secondary coil has a greater number of turns than the primary (Ns > Np), the voltage is stepped up (Vs > Vp). This type of arrangement is called a step-up transformer.”