JEE Mains · Physics · STD 12 - 4. Moving charges and magnetism
An insulated wire is wound so that it forms a flat coil with \(N = 200\) turns. The radius of the innermost turn is \(r_1 = 3\) cm, and of the outermost turn \(r_2 = 6\) cm. If \(20\) mA current flows in it then the magnetic moment will be \(\alpha \times 10^{-2}\) A.m\(^2\). The value of \(\alpha\) is _____.
- A \(4.4\)
- B \(2.64\)
- C \(3.25\)
- D \(1.2\)
Answer & Solution
Correct Answer
(B) \(2.64\)
Step-by-step Solution
Detailed explanation
Let the number of turns per unit radial width be \(n = \dfrac{N}{r_2 - r_1}\). Consider an elemental ring of radius \(r\) and width \(dr\). The number of turns in this element is \(dN = n \, dr\). The magnetic moment of this elemental ring is…
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