Question

The magnetic field at perpendicular distance '\(r\)' from a long wire carrying current '\(I\)' is '\(B\)'. The magnetic field at perpendicular distance '\(2r\)' from the same wire is

• A. \(\frac{B}{4}\)
• B. \(\frac{B}{2}\)
• C. \(2B\)
• D. \(4B\)

Hint:

\(B=\dfrac{\mu_0I}{2\pi r}\), so \(B\propto\dfrac1r\).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept
The field of a long straight current-carrying wire at distance \(r\) is \(B=\dfrac{\mu_0I}{2\pi r}\).

Step 2: Detailed Explanation
At \(2r\): \(B'=\dfrac{\mu_0I}{2\pi(2r)}=\dfrac B2\).

Final Answer:
The field becomes \(B/2\), option (B). \[ \boxed{\dfrac B2\ \text{(B)}} \]