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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

Two parallel wires are separated by a distance of 2.0 cm and carry...

Two parallel wires are separated by a distance of 2.0 cm2.0 \text{ cm} and carry equal currents of 10 A10 \text{ A} in the same direction. Determine the magnitude of the magnetic field at a point located 2.0 cm2.0 \text{ cm} away from each of the two wires.

Options

  1. A2.0×10−4 T2.0 \times 10^{-4} \text{ T}
  2. B1.7×10−4 T1.7 \times 10^{-4} \text{ T}
  3. C1.4×10−4 T1.4 \times 10^{-4} \text{ T}
  4. D1.0×10−4 T1.0 \times 10^{-4} \text{ T}

Correct answer

B. 1.7×10−4 T1.7 \times 10^{-4} \text{ T}

Step-by-step solution

Let the two wires be at points A and B, and the observation point be P.

Since the distance between the wires is 2.0 cm2.0 \text{ cm} and point P is 2.0 cm2.0 \text{ cm} away from both wires, triangle PAB is an equilateral triangle with side length a=2.0 cm=0.02 ma = 2.0 \text{ cm} = 0.02 \text{ m}.

The magnitude of the magnetic field at P due to each wire is:

B1=B2=μ0I2πaB_1 = B_2 = \dfrac{\mu_0 I}{2 \pi a}

Substituting the given values:

B1=4π×10−7×102π×0.02=10−4 TB_1 = \dfrac{4 \pi \times 10^{-7} \times 10}{2 \pi \times 0.02} = 10^{-4} \text{ T}

The magnetic field vectors B⃗1\vec{B}_1 and B⃗2\vec{B}_2 are perpendicular to the position vectors connecting the wires to point P. Since the angle between these position vectors is 60^{}^{{}^{\circ}} and the currents are in the same direction, the angle between B⃗1\vec{B}_1 and B⃗2\vec{B}_2 is also 60^{}^{{}^{\circ}}.

The resultant magnetic field BnetB_{net} is given by vector addition:

B_{net} = \sqrt{B_1^2 + B_2^2 + 2 B_1 B_2 \cos 60^{}^{{}^{\circ}}}

Bnet=B12+B12+2B12(12)=3B1B_{net} = \sqrt{B_1^2 + B_1^2 + 2 B_1^2 \left(\dfrac{1}{2}\right)} = \sqrt{3} B_1

Bnet=3×10−4 T≈1.7×10−4 TB_{net} = \sqrt{3} \times 10^{-4} \text{ T} \approx 1.7 \times 10^{-4} \text{ T}
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