In the context of magnets and magnetic fields, all of the following can produce a magnetic field except which one?

• A. A permanent bar magnet
• B. A stationary electric charge
• C. A straight wire carrying a steady current
• D. A solenoid with current flowing through its coils

Answer: (B)

Verified step by step guidance

1. Recall the sources of magnetic fields: magnetic fields are produced by moving electric charges (currents) or intrinsic magnetic moments of particles, such as those in permanent magnets.
2. Analyze each option: a permanent bar magnet produces a magnetic field due to aligned magnetic domains; a straight wire carrying a steady current produces a magnetic field due to moving charges; a solenoid with current flowing through its coils produces a magnetic field similar to a bar magnet.
3. Consider the stationary electric charge: since it is not moving, it does not produce a magnetic field, only an electric field.
4. Conclude that among the options, only a stationary electric charge does not produce a magnetic field.
5. Summarize that magnetic fields arise from moving charges or intrinsic magnetic moments, not from charges at rest.