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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

A current of 10 A is maintained in a long wire directed along the...

A current of 10 A10 \text{ A} is maintained in a long wire directed along the positive zz-axis. Determine the magnetic field B⃗\vec{B} at the point (1 m,0,0)(1 \text{ m}, 0, 0).

Options

  1. A2μT2 \mu\text{T} along the positive yy-axis
  2. B4μT4 \mu\text{T} along the positive yy-axis
  3. C4μT4 \mu\text{T} along the negative yy-axis
  4. D2μT2 \mu\text{T} along the negative yy-axis

Correct answer

A. 2μT2 \mu\text{T} along the positive yy-axis

Step-by-step solution

The magnetic field due to a long straight current-carrying wire is given by B=μ0I2πrB = \dfrac{\mu_0 I}{2 \pi r}

Given I=10 AI = 10 \text{ A} and perpendicular distance r=1 mr = 1 \text{ m}

Substituting the values:

B=4π×10−7×102π×1=2×10−6 T=2μTB = \dfrac{4 \pi \times 10^{-7} \times 10}{2 \pi \times 1} = 2 \times 10^{-6} \text{ T} = 2 \mu\text{T}

The direction of the magnetic field is given by the cross product dl⃗×r⃗d\vec{l} \times \vec{r}

Since the current is along the positive zz-axis (dl⃗∥k^d\vec{l} \parallel \hat{k}) and the position vector is along the positive xx-axis (r⃗=i^\vec{r} = \hat{i}), the direction is along k^×i^=j^\hat{k} \times \hat{i} = \hat{j}

Thus, the magnetic field is 2μT2 \mu\text{T} along the positive yy-axis
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