Answer: mu0 nI.
- A mu0 n
- B mu0 nI
- C mu0 I/n
- D mu0 n2 I
Correct answer: B. mu0 nI
Explanation: Solenoid: B = mu0 nI (n = turns per unit length). This is uniform inside a long solenoid.
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.