Question:
A long straight wire along the Z-axis carries a current I in the negative Z-direction. The magnetic vector field vecB at a point having coordinates (x,y) in the Z=0 plane is
A long straight wire along the Z-axis carries a current I in the negative Z-direction. The magnetic vector field vecB at a point having coordinates (x,y) in the Z=0 plane is
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Always determine direction of magnetic field using right-hand thumb rule before writing vector form.
Updated On: Mar 20, 2026
- \( \dfrac{\mu_0 I}{2\pi(x^2+y^2)}(y\hat{i}-x\hat{j}) \)
- \( \dfrac{\mu_0 I}{2\pi(x^2+y^2)}(x\hat{i}+y\hat{j}) \)
- \( \dfrac{\mu_0 I}{2\pi(x^2+y^2)}(-x\hat{i}-y\hat{j}) \)
- (mu₀ I)/(2π(x²+y²))(-yhati+xhatj)
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The Correct Option is A
Solution and Explanation
Step 1: Magnetic field due to long straight wire: B = (mu₀ I)/(2π r)
Step 2: Direction is given by right-hand thumb rule. Since current is along negative z-axis, field circulates clockwise.
Step 3: Vector form: B = (mu₀ I)/(2π(x²+y²))(yhati-xhatj)
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