Magnetic Field of a Current-Carrying Loop?

📌 CONCEPT: The magnetic field inside a current-carrying loop depends on the direction of the current and the shape of the loop. When the current flows in one direction, it creates a magnetic field that is confined within the loop. Reversing the current direction results in a change in the magnetic field lines within the loop.

📐 RULE / FORMULA: The magnetic field inside the loop is given by B = μoI / (2πr), where μo is the magnetic constant, I is the current, and r is the radius of the loop. However, this formula is applicable only when the current flows in a single turn loop.

💡 WORKED EXAMPLE: Suppose a circular loop of radius 0.1 m carries a current of 5 A. When the current flows in one direction, the magnetic field inside the loop is B = (4π × 10^-7 Tm/A) × 5 A / (2π × 0.1 m) = 10^-5 T. Reversing the current direction does not affect the magnitude of the magnetic field, but it changes the direction of the field lines.

⚠️ COMMON MISTAKE: Students often confuse the direction of the magnetic field with the direction of the current flow. They should remember that the magnetic field lines always form concentric circles inside a current-carrying loop, and reversing the current direction changes the direction of these field lines.