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A circular coil consists 70 closely wound turns and has a radius of 10 ~cm . An externally produced magnetic field of magnitude 2 10⁻³ ~T is applied perpendicular to the coil. The net flux through the coil is found to vanish when the current in the coil is 2.2 ~A . The inductance of the coil is

Options

  1. A2 mH
  2. B3 mH
  3. C4 mH
  4. D1.5 mH

Correct answer

A. 2 mH

Step-by-step solution

Given, number of turns in the circular coil, N=70, r=10 ~cm =10⁻¹ ~m B=2 10⁻³ ~T =0^ Magnetic flux, =N B A =70 2 10⁻³ r^2 0^ =140 10⁻³ (10⁻¹ )^2=140 10⁻⁵=140 22 7 10⁻⁵=4.4 10⁻³ ~Wb We know that, =L IL= I = 4.4 10⁻³ 2.2 =2 10⁻³ H =2 mH

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