Answer: mu0 I/(2 R).
- A mu0 I/(4 pi R)
- B mu0 I/(2 R)
- C mu0 I/(R)
- D 2 mu0 I/R
Correct answer: B. mu0 I/(2 R)
Explanation: B at center of circular loop = mu0 I/(2R). This comes from Biot-Savart law integration around the full circle.
The magnetic field around a long straight current-carrying wire forms concentric circles, with direction given by the right-hand rule (point thumb along I, fingers curl in the direction of B).
Concept context
Magnetic force on moving charges and currents, the Biot-Savart law, Ampere's law, and the cyclotron - how electric currents create and respond to magnetic fields.