Choose the correct answer statements from the following:A. Magnetic f…

The correct answer is Option (4) → A, C and D only

(A) Magnetic field lines due to a straight wire carrying current, are circles concentric with the wire. — Correct. By symmetry the field has the same magnitude all round the wire and is tangential, \( B = \frac{\mu_0 I}{2\pi r} \), so the lines are concentric circles with their sense given by the right-hand rule.

(B) Bohr magneton is the maximum value of the magnetic moment of an electron moving around the central nucleus. — Incorrect. The orbital magnetic moment is \( \mu_l = \frac{el}{2m} \) with \( l = \frac{nh}{2\pi} \). Its smallest value, for \( n = 1 \), is the Bohr magneton \( \mu_B = 9.27\times10^{-24}\,\mathrm{J\,T^{-1}} \); it is the minimum, not the maximum.

(C) Ampere’s circuital law is not independent of Biot-savart law. — Correct. Ampere’s law can be derived from the Biot-Savart law, in the same way as Gauss’s law follows from Coulomb’s law.

(D) Dip is the angle that the total magnetic field of the earth makes with the surface of the earth. — Correct. This is the definition of the angle of dip, measured between the total field \( B_E \) and its horizontal component.

Note: Statements (A) and (C) of this question are from the latest textbook (2026-27). Statement (B), on the Bohr magneton, and statement (D), on the angle of dip, are printed only in the pre-rationalised textbook (2022-23). They were removed from the latest book, and they also appear to be out of the CUET 2026 syllabus.

NCERT (2026-27):
Ampere’s Circuital Law – “… Thus, the lines of constant magnitude of magnetic field form concentric circles. Notice now, in Fig. 4.1(c), the iron filings form concentric circles. These lines called magnetic field lines form closed loops.”

Points to Ponder – “… 4. Ampere’s Circuital law is not independent of the Biot-Savart law. It can be derived from the Biot-Savart law.”

NCERT (Pre-rationalised edition, 2022-23):
Summary – “… The smallest value of μ_l is called the Bohr magneton μ_B and it is μ_B = 9.27×10^–24 J/T”

Magnetic Declination and Dip – “… Thus, dip is the angle that the total magnetic field B_E of the earth makes with the surface of the earth.”