A solenoid has a core of a material with a relative permeability of 500. The windings of the solenoid are insulated from the core and carry a current of 0.5 A. If the number of turns is 2000 per metre, the magnetic intensity is
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \( 10^{3}\,\mathrm{A\,m^{-1}} \)
The magnetic intensity \( H \) inside a solenoid is set by the free current in the windings alone; the core material does not enter it.
\( \displaystyle H = n\,I \)
\( n = 2000\,\mathrm{m^{-1}} \)
\( I = 0.5\,\mathrm{A} \)
\( \displaystyle H = 2000 \times 0.5 = 1000\,\mathrm{A\,m^{-1}} = 10^{3}\,\mathrm{A\,m^{-1}} \)
The relative permeability 500 is needed only for the field in the core, \( B = \mu_0\mu_r H \), and the magnetisation.
Note: NTA picked this question from an NCERT (2026-27) example and changed the figures. Do not ignore NCERT while practising numericals.
NCERT (2026-27):
Magnetisation and Magnetic Intensity – …
