Identify the correct statements among the following.
A. The main reason for preferring use of ac voltage over dc voltage is that ac voltages can be easily and efficiently converted from one voltage to another by means of transformers.
B. The electrical energy can also be transmitted economically over long distances using transformer.
C. The ac circuits exhibit characteristics which are exploited in many devices of daily use.
D. The ac current is an electrical quantity displaying simple harmonic time dependence.
Choose the correct answer from the option(s) given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → A, B, C and D
All four statements describe why alternating current is used so widely.
(A) The main reason for preferring use of ac voltage over dc voltage is that ac voltages can be easily and efficiently converted from one voltage to another by means of transformers. — Correct. A transformer works only with a changing flux, so it can step an ac voltage up or down, but not a steady dc voltage.
(B) The electrical energy can also be transmitted economically over long distances using transformer. — Correct. Stepping the voltage up lowers the current for the same power, which cuts the \( I^{2}R \) loss in the transmission lines.
(C) The ac circuits exhibit characteristics which are exploited in many devices of daily use. — Correct. The reactances of inductors and capacitors depend on frequency, which is used in tuning circuits of radios, filters and chokes.
(D) The ac current is an electrical quantity displaying simple harmonic time dependence. — Correct. \( i = i_0\sin\omega t \) varies sinusoidally with time.
NCERT (2026-27):
Introduction – “… The main reason for preferring use of ac voltage over dc voltage is that ac voltages can be easily and efficiently converted from one voltage to the other by means of transformers. Further, electrical energy can also be transmitted economically over long distances. AC circuits exhibit characteristics which are exploited in many devices of daily use.”
Introduction – “… Still, the abbreviation ac to designate an electrical quantity displaying simple harmonic time dependance has become so universally accepted that we follow others in its use.”