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COMEDK · Physics · 21. Magnetic Effects of Current

In a particular case \(X\), a certain length of insulated copper wire is bent to form double loops of equal radii. In another case Y the same copper wire is bent to form three loops of equal radii. If the same steady current is passed through the copper wire in both the cases, the ratio of magnetic field at the centre in the case X to that in case Y is:

  1. A \(\dfrac{1}{9}\)
  2. B \(\dfrac{1}{4}\)
  3. C \(\dfrac{9}{4}\)
  4. D \(\dfrac{4}{9}\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(\dfrac{4}{9}\)

Step-by-step Solution

Detailed explanation

Let \(L\) be the total length of the wire. In case \(X\), the wire is bent into \(n_1 = 2\) loops of radius \(r_1\). The circumference of these loops is \(2 \times (2 \pi r_1) = L\), so \(r_1 = \dfrac{L}{4 \pi}\). The magnetic field at the center of \(n_1\) loops is…