JEE Mains · Physics · STD 12 - 4. Moving charges and magnetism
A long straight wire of radius ' \(a\) ' carries a steady current I. The current is uniformly distributed across its cross section. The ratio of the magnetic field at \(\frac{a}{2}\) and \(2\)a from axis of the wire is _______.
- A \(1: 4\)
- B \(4: 1\)
- C \(1: 1\)
- D \(3: 4\)
Answer & Solution
Correct Answer
(C) \(1: 1\)
Step-by-step Solution
Detailed explanation
\(\mathrm{B}_1 2 \pi \frac{\mathrm{a}}{2}=\mu_0 \frac{\mathrm{I}}{4}\) \(\mathrm{~B}_1=\frac{\mu_0 \mathrm{I}}{4 \pi \mathrm{a}}\) \(\mathrm{B}_2 2 \pi 2 \mathrm{a}=\mu_0 \mathrm{I}\) \(\mathrm{B}_2=\frac{\mu_{\mathrm{v}} \mathrm{I}}{4 \pi \mathrm{a}}\)
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