Q160 / 180 · KCET 2012 · Physics

Magnetic field at a distance $r$ from an infinitely long straight conductor carrying a steady current varies as

  • A
    $\frac{1}{\sqrt{r}}$
  • B
    $\frac{1}{r^{2}}$
  • Correct answer
    C
    $\frac{1}{r}$
  • D
    $\frac{1}{r^{3}}$

Solution

We have $B=\frac{\mu_{0}}{4 \pi} \cdot \frac{2 l}{r}$ $\therefore \quad \mathrm{B} \propto \frac{1}{\mathrm{r}}$

Hence, the correct answer is option: 'C'.

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