Magnetic Effects & Magnetism

JEE Main level, single correct, medium

255 of 276

Question 255 of 276

An iron rod of volume 10−3m3{10}^{-3}{m}^{3} and relative permeability 10001000 is placed as core in a solenoid with10turnscm−110turns{cm}^{-1} . If a current of 0.5A0.5A is passed through the solenoid, then the magnetic moment of the rod will be :

Show answer and solution

Answer: (B) 5×102Am25\times {10}^{2}{Am}^{2}

Given,
Volume of iron rod is, V=10−3m3V={10}^{-3}{m}^{3}
Relative permeability, μr=1000{\mu }_{r}=1000
No of turns per unit length of solenoid is, n=Nl=10turnscm−1=1000turnsm−1n=\dfrac{N}{l}=10turns{cm}^{-1}=1000turns{m}^{-1}
Current through the solenoid is, i=0.5Ai=0.5A
Magnetic moment of an iron core solenoid is given by,
M=(μr−1)NiAM=({\mu }_{r}-1)NiA
⇒M=(μr−1)NiVl=(μr−1)NliV\Rightarrow M=\left({\mu }_{r}-1\right)Ni\dfrac{V}{l}=\left({\mu }_{r}-1\right)\dfrac{N}{l}iV
⇒M=(1000−1)×1000×0.5×10−3\Rightarrow M=\left(1000-1\right)\times 1000\times 0.5\times {10}^{-3}
⇒M=499.5≈500Am2\Rightarrow M=499.5\approx 500A{m}^{2}

JEE Main question paper PDF

Open a shift to read the full paper on this page, or download it.

JEE Main 2025 Apr 2 Shift 1 question paper

Open Download PDF

Opening paper…

Explain it as a whiteboard videoStep-by-step, in Hinglish or English. Your first video needs no login.Solved it on paper but got it wrong?Upload a photo of your working. Mistake Doctor marks the exact line that broke.

More Physics practice

JEE Main Physics practice question on Magnetic Effects & Magnetism (Magnetic Moment), with the answer and a step-by-step solution. Scan a question from your own book or paper to get a whiteboard video.