The magnetic field at the centre of a circular current loop of radius R carrying current I is:

1. Integrate Biot-Savart around the loop; symmetry leaves only the axial component. 2. At the centre of a coil of N turns: B = μ₀ N I / (2 R). For N = 1: B = μ₀ I / (2 R). 3. Direction by right-hand rule (curl fingers along I → thumb gives B direction). _Source: NCERT Class 12 Physics Ch 4 §4.6 Field on the Axis of a Circular Coil_