Question

Two long straight wires are set parallel to each other. Each carries a current in the same direction and the separation between them is $2r$. The intensity of the magnetic field mid-way between them is}

• A. $\frac{\mu_0 I}{\pi r}$
• B. $\frac{\mu_0 I}{2\pi r}$
• C. 0
• D. $\frac{2\mu_0 I}{\pi r}$

Hint:

For two parallel currents in the same direction, fields at the midpoint cancel.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Magnetic field due to a long straight wire: $B = \frac{\mu_0 I}{2\pi r}$.
Step 2: Detailed Explanation:
At the midpoint, distance from each wire is $r$. Magnetic fields due to each wire are equal in magnitude $B = \frac{\mu_0 I}{2\pi r}$ but opposite in direction (by right-hand rule). Hence, net magnetic field is zero.
Step 3: Final Answer:
The magnetic field is zero.