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NEET2026PhysicsChapterActual

A long tightly wound solenoid is used in a laboratory to generate a uniform magnetic field of 25.12 mT at its center. If the solenoid has 500 turns per 10 cm of its length, what is the magnitude of the steady current flowing through it? (Take = 3.14 )

Options

  1. A8 A
  2. B40 A
  3. C4 A
  4. D400 A

Correct answer

C. 4 A

Step-by-step solution

The magnetic field at the center of a long tightly wound solenoid is given by the formula: B = ₀ n I where n is the number of turns per unit length and I is the current. Given: B = 25.12 mT = 25.12 10⁻³ T n = 500 10 cm = 500 10 10⁻² m = 5000 turns/m ₀ = 4 10⁻⁷ T m/A Substituting the values into the formula: 25.12 10⁻³ = (4 3.14 10⁻⁷) 5000 I 25.12 10⁻³ = 12.56 10⁻⁷ 5000 I 25.12 10⁻³ = 6.28 10⁻³ I I = 25.12 10⁻³ 6.28 10⁻³ I = 4 A Answer: 4 A

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