Home › UP Board Class 12 › Physics › Moving Charges and Magnetism › A circular loop of radius R carries current I. T…
A circular loop of radius R carries current I. The magnitude of the magnetic field at its centre is
Aμ₀I / (4πR)
Bμ₀I / R
Cμ₀I / (2R)
Dμ₀I / (4R)
Answer & Solution
Correct answer: C. μ₀I / (2R)
1. The Biot-Savart contribution from each element of the loop adds constructively at the centre.
2. Each element dl is perpendicular to the radius r̂, so |dl × r̂| = dl.
3. Integrating around the full loop: B = μ₀I/(4π) · ∫dl/R² = μ₀I/(4πR²) · 2πR.
4. Simplify to B = μ₀I/(2R).
_Source: NCERT Class 12 Physics Ch 4 "Moving Charges and Magnetism", §4.5_
Related questions
An electron and a proton enter a magnetic field with the same kinetic energy, perpendiculaA galvanometer is converted into an ammeter of higher range by connecting:The work done by a static magnetic force on a moving charge is:Magnetic field at a point on the axis of a circular loop, far from the loop (distance x ≫ The dimensional formula of the magnetic field B (in SI units of tesla) is:A cyclotron of magnetic field B accelerates positive charges of mass m, charge q. The cyclTorque on a magnetic dipole (current loop) of moment m placed in a uniform field B at anglTwo long parallel wires carry currents I₁ and I₂ in the SAME direction, separated by dista