Moving Charges and Magnetism - Result Question 53

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54. The magnetic induction at a point $P$ which is at a distance of $4 cm$ from a long current carrying wire is $10^{-3} T$. The field of induction at a distance $12 cm$ from the current will be

======= ####54. The magnetic induction at a point $P$ which is at a distance of $4 cm$ from a long current carrying wire is $10^{-3} T$. The field of induction at a distance $12 cm$ from the current will be

3e0f7ab6f6a50373c3f2dbda6ca2533482a77bed:content/english/neet-pyq-chapterwise/physics/moving-charges-and-magnetism/moving-charges-and-magnetism—result-question-53.md (a) $3.33 \times 10^{-4} T$

(b) $1.11 \times 10^{-4} T$

(c) $3 \times 10^{-3} T$

(d) $9 \times 10^{-3} T$

[1990]

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Answer:

Correct Answer: 54. (a)

Solution:

(a) $B=\frac{\mu_0 I}{2 \pi r} \Rightarrow B \propto \frac{1}{r}$

As the distance is increased to three times, the magnetic induction reduces to one third. Hence,

$B=\frac{1}{3} \times 10^{-3}$ tesla $=3.33 \times 10^{-4}$ tesla