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Concepts Of Physics MCQ Edition [Volume 2]
Exam
Concepts Of Physics MCQ Edition [Volume 2]
Subject
Physics
Chapter
Magnetic Field due to a Current

Concepts Of Physics MCQ Edition [Volume 2] · Physics · Magnetic Field due to a Current

Inside a long solenoid that carries a current of 5.00 A , the...

Inside a long solenoid that carries a current of 5.00 A5.00 \text{ A}, the magnetic field BB is found to be 3.14×10−2 T3.14 \times 10^{-2} \text{ T}. Determine the number of turns per unit length for this solenoid.

Options

  1. A10000 turns/m10000 \text{ turns/m}
  2. B500 turns/m500 \text{ turns/m}
  3. C20000 turns/m20000 \text{ turns/m}
  4. D5000 turns/m5000 \text{ turns/m}

Correct answer

D. 5000 turns/m5000 \text{ turns/m}

Step-by-step solution

The magnetic field inside a long solenoid is given by the formula:

B=μ0nIB = \mu_{0} n I

Rearranging for the number of turns per unit length nn:

n=Bμ0In = \dfrac{B}{\mu_{0} I}

Substituting the given values B=3.14×10−2 TB = 3.14 \times 10^{-2} \text{ T}, I=5.00 AI = 5.00 \text{ A}, and μ0=4π×10−7 T⋅m/A\mu_{0} = 4\pi \times 10^{-7} \text{ T}\cdot\text{m/A}:

n=3.14×10−24π×10−7×5.00n = \dfrac{3.14 \times 10^{-2}}{4\pi \times 10^{-7} \times 5.00}

Using π≈3.14\pi \approx 3.14:

n=3.14×10−24×3.14×10−7×5.00n = \dfrac{3.14 \times 10^{-2}}{4 \times 3.14 \times 10^{-7} \times 5.00}

n=10−220×10−7n = \dfrac{10^{-2}}{20 \times 10^{-7}}

n=10−22×10−6n = \dfrac{10^{-2}}{2 \times 10^{-6}}

n=0.5×104=5000 turns/mn = 0.5 \times 10^{4} = 5000 \text{ turns/m}
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