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NEET 2021 · Ampere's Law, Cylinders, Solenoid & Toroid

Ampere's Law, Cylinders, Solenoid & Toroid question from NEET 2021

Q36NEET 2021Easy

Ampere's Law, Cylinders, Solenoid & Toroid

A thick current carrying cable of radius 'R' carries current 'I' uniformly distributed across its cross section. The variation of magnetic field B(r) due to the cable with the distance 'r' from the axis of the cable is represented by:

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Answer: (d)

  1. Inside (r<Rr < R): B=μ0Ir2πR2∝rB = \frac{\mu_0 I r}{2\pi R^2} \propto r.
  2. Outside (r>Rr > R): B=μ0I2πr∝1rB = \frac{\mu_0 I}{2\pi r} \propto \frac{1}{r}.
  3. Graph rises linearly to a peak at r=Rr = R and then falls off.
  4. So the answer is (d).
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