WBJEE · Physics · Magnetic Effects of Current
The magnetic field due to a current in a straight wire segment of length \(L\) at a point on
its perpendicular bisector at a distano \(r(r>>L)\)
- A decreases as \(\frac{1}{r}\)
- B decreases as \(\frac{1}{r^{2}}\)
- C decreases as \(\frac{1}{r^{3}}\)
- D approaches a finite limit as \(r \rightarrow \infty\)
Answer & Solution
Correct Answer
(B) decreases as \(\frac{1}{r^{2}}\)
Step-by-step Solution
Detailed explanation
By Biot-Savart's law, the magnetic field due to a current carrying wire is \[ B=\frac{\mu_{0}}{4 \pi} \cdot \frac{I d l \sin \theta}{r^{2}} \] So, \[ B=\frac{1}{r^{2}} \] So, the magnetic field due to current decreases as inverse square of distance of the point of observation.
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