Identify the correct statements among the following.
A. In a step down transformer, voltage across secondary coil is more than the primary coil.
B. In a step up transformer, primary coil current is more than the secondary coil current.
C. In a step up transformer, current in secondary coil is more than the primary coil.
D. In a step down transformer, secondary coil has less number of turns than the primary coil.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → B and D only
In an ideal transformer \( V_s/V_p = N_s/N_p \), and since the power is the same on both sides, \( V_pI_p = V_sI_s \): the current changes in the opposite ratio to the voltage.
(A) In a step down transformer, voltage across secondary coil is more than the primary coil. — Incorrect. A step-down transformer lowers the voltage, so \( V_s \lt V_p \).
(B) In a step up transformer, primary coil current is more than the secondary coil current. — Correct. The voltage is raised, so the current is lowered: \( I_s \lt I_p \).
(C) In a step up transformer, current in secondary coil is more than the primary coil. — Incorrect. This contradicts (B).
(D) In a step down transformer, secondary coil has less number of turns than the primary coil. — Correct. \( V_s \lt V_p \) requires \( N_s \lt N_p \).
NCERT (2026-27):
Transformers – “… 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. However, in this arrangement, there is less current in the secondary than in the primary (Np/Ns < 1 and Is < Ip). … If the secondary coil has less turns than the primary (Ns < Np), we have a step-down transformer. In this case, Vs < Vp and Is > Ip.”