Strictly speaking, Oersted is the CGS unit of magnetic field strength (H). However, as it is the only relevant magnetic unit provided among the choices, it is the expected answer.
Q. 122. The frequency of the AC power supply used in India is:
(A) 70 Hz
(B) 60 Hz
(C) 50 Hz
(D) 40 Hz
Answer:
(C) 50 Hz
Explanation:
In India, the standard grid frequency of the alternating current (AC) domestic power supply is 50 Hertz.
Q. 123. Metals that get magnatised by orientation of atomic magnetic moments in external magnetic field are called:
(A) Ferromagnetic
(B) Paramagnetic
(C) Diamagnetic
(D) Antimagnetic
Answer:
(A) Ferromagnetic
Explanation:
Ferromagnetic materials are strongly magnetized in an external magnetic field due to the powerful parallel alignment of their atomic magnetic moments (domains).
Q. 124. Sound travels at $332~m/s$ in air. It means that:
(A) The source of sound moves 332 m in one second
(B) The listener moves 332 m in one second
(C) Air moves 332 m in one second
(D) The disturbance in the air moves 332 m in one second
Answer:
(D) The disturbance in the air moves 332 m in one second
Explanation:
Sound propagates as a mechanical wave through a medium. It is the disturbance (the wave of compressions and rarefactions) that travels at 332 m/s, not the physical air molecules or the source itself.
Q. 125. When ice melts its temperature:
(A) remains constant
(B) increases
(C) decreases
(D) either increases or decreases
Answer:
(A) remains constant
Explanation:
During a phase change (like melting), the temperature of the substance remains constant because the supplied heat energy is used entirely to break the intermolecular bonds (latent heat of fusion).
