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Moving Charges and Magnetism
Magnetic Field at Centre of Circular Coil
1 question from 1 paper, each with its answer.
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Concepts tested
- Rewinding the same wire into more turns
All Questions
2002 AIPMT 1 question
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The magnetic field of given length of wire for single turn coil at its centre is 'B' then its value for two turns coil for the same wire is : -For a single turn of radius R: $B_1 = B = \dfrac{\mu_0I}{2R}$
The same wire is wound into 2 turns, so the length stays the same: $2 \times 2\pi r = 2\pi R \Rightarrow r = \dfrac{R}{2}$
For N turns: $B_2 = \dfrac{\mu_0NI}{2r} = \dfrac{\mu_0(2I)}{2(R/2)} = 4 \times \dfrac{\mu_0I}{2R}$
$B_2 = 4B$
In general, rewinding into n turns gives $n^2B$.