Answer: 4 × 10⁻³ T.
- A 4 × 10⁻³ T
- B 8 × 10⁻³ T
- C 2 × 10⁻³ T
- D 1 × 10⁻³ T
Correct answer: A. 4 × 10⁻³ T
Explanation: B = μ0 N I/(2πr) = (4π×10⁻⁷ × 500 × 4)/(2π × 0.2) ≈ 4 × 10⁻³ T.
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.