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QJEEM21Ph2e60: JEE Main 2021 Physics - Class 12 JEEM21Ph2e60 Solution: A coil having N turns is wound tightly in the form of a spiral…

A coil having N turns is wound tightly in the form of a spiral with inner and outer radii 'a' and 'b' respectively. Find the magnetic field at centre, when a current I passes through coil:

Multiple Choice Options

  • A μ0IN2(b−a)loge(ba)
  • B μ0I8[a+ba−b]
  • C μ0I4(a−b)[1a−1b]
  • D μ0I8(a−ba+b)

Step-by-Step Verified Solution

JEE Main 2021 (Online) 31st August Morning Shift Physics - Magnetic Effect of Current Question 106 English Explanation
No. of turns in dx width = Nb−adx

∫dB=∫ab(Nb−a)dxμ0I2x

B=Nμ0i2(b−a)ln⁡(ba)

Option (a)

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