Join the Most Relevant JEE Main 2025 Test Series & get 99+ percentile! Join Now
Search any question & find its solution
Question: Answered & Verified by Expert
A toroid has \( 500 \) turns per metre length. If it carries a current of \( 2 \mathrm{~A} \), the magnetic energy
density inside the toroid is
PhysicsMagnetic Effects of CurrentKCETKCET 2019
Options:
  • A \( 6.28 \mathrm{~J} / \mathrm{m} 3 \)
  • B \( 0.628 \mathrm{~J} / \mathrm{m} 3 \)
  • C \( 3.14 \mathrm{~J} / \mathrm{m} 3 \)
  • D \( 0.314 \mathrm{~J} / \mathrm{m} 3 \)
Solution:
2699 Upvotes Verified Answer
The correct answer is: \( 0.628 \mathrm{~J} / \mathrm{m} 3 \)
(B)Sol. Magnetic field inside a toroid
\[
\mathrm{B}=\mu_{o} \mathrm{nl}
\]
Magnetic energy density inside the toroid is
\[
\begin{array}{l}
u_{o}=\frac{B^{2}}{2 \mu_{o}}=\frac{\mu_{o}^{2} n^{2} I^{2}}{2 \mu_{o}}=\frac{\mu_{o} n^{2} I^{2}}{2} \\
=\frac{4 \Pi \times 10^{-7} \times(500)^{2} \times 2^{2}}{2}=0.628 \mathrm{~J} \mathrm{~m}^{-3}
\end{array}
\]

Looking for more such questions to practice?

Download the MARKS App - The ultimate prep app for IIT JEE & NEET with chapter-wise PYQs, revision notes, formula sheets, custom tests & much more.