Which of the following statement(s) is/are incorrect?
(A) A current carrying loop may act as a magnetic dipole whose magnetic moment may depend on its area and the number of turns.
(B) A linear solenoid carrying current, may act as a bar magnet.
(C) The magnetic lines of forces due to the current carrying solenoid makes closed curves like in a bar magnet.
(D) The magnetic field inside a solenoid is perpendicular to its axis.
Choose the correct answer from the given options:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (D) only
Here each statement is labelled by whether it is a true or a false statement; the question asks for the false ones.
(A) A current carrying loop may act as a magnetic dipole whose magnetic moment may depend on its area and the number of turns. — True statement. A loop of \( N \) turns, area \( A \) and current \( I \) is a magnetic dipole of moment \( m = NIA \).
(B) A linear solenoid carrying current, may act as a bar magnet. — True statement. Its field outside resembles that of a bar magnet, with one end acting as a north pole and the other as a south pole.
(C) The magnetic lines of forces due to the current carrying solenoid makes closed curves like in a bar magnet. — True statement. Magnetic field lines are always closed curves; they pass through the inside of the solenoid (or of the magnet) and return outside.
(D) The magnetic field inside a solenoid is perpendicular to its axis. — False statement. Inside a long solenoid the field is uniform and parallel to the axis, \( B = \mu_0 n I \).
Only (D) is incorrect, which is Option (4).
NCERT (2026-27):
The Solenoid – “… In Fig. 4.15(b), we see that the field at the interior mid-point P is uniform, strong and along the axis of the solenoid.”
Bar Magnet as an Equivalent Solenoid – “… Thus, a bar magnet and a solenoid produce similar magnetic fields.”