JEE MainPhysicsMagnetic Effects of Current
A wire carrying a steady current I is bent into three segments in 3D space: a semi-infinite straight line from (R, 0, + ) to (R, 0, 0) , a quarter-circular arc in the xy -plane from (R, 0, 0) to (0, R, 0) , and another semi-infinite straight line from (0, R, 0) to (0, R, + ) . The magnitude of the net magnetic field at the origin (0, 0, 0) is:
Options
- A₀ I 8 R (4 + )
- B₀ I 8 R 8 + ^2
- C₀ I 8 R
- D₀ I 8 R 16 + ^2
Correct answer
B. ₀ I 8 R 8 + ^2
Step-by-step solution
The total magnetic field at the origin is the vector sum of the magnetic fields produced by the three segments of the wire. For the first semi-infinite straight wire from (R, 0, + ) to (R, 0, 0) , the current flows in the - k direction. The position vector of the origin relative to the end of this wire is -R i . Using the Biot-Savart law, the magnetic field at the origin is B ₁ = ₀ I 4 R j . For the quarter-circular arc in the xy -plane from (R, 0, 0) to (0, R, 0) , the current flows in a counter-clockwise directio