ExamBro
ExamBro
JEE Mains · Physics · STD 12 - Magnetism and matter
  • JEE Mains 2025
  • Hard
  • MCQ


A bar magnet has total length \(2 l=20\) units and the field point \(P\) is at a distance \(\mathrm{d}=10\) units from the centre of the magnet. If the relative uncertainty of length measurement is \(1 \%\), then uncertainty of the magnetic field at point P is :

Pick an option to check your answer.
Verified Solution

Answer & Solution

Correct Answer

(A) \(4 \%\)

Step-by-step Solution

Detailed explanation


Magnetic field at \(P, B=\frac{\mu_0}{4 \pi} \frac{m(2 l)}{r^3}\), where \(m\) is the pole strength
\(\begin{aligned}
\Rightarrow\left(\frac{\Delta B}{B} \times 100\right) & =\left(\frac{\Delta l}{l}\right) \times 100+3\left|\frac{\Delta r}{r}\right| \times 100 \\
& =1 \%+3 \%=4 \%
\end{aligned}\)
Same subject
Explore more questions on app