Question

Which of the following is not a source of magnetostatic fields?

• A. A dc current in a wire
• B. A permanent magnet
• C. An electric field linearly changing with time
• D. A charged disk rotating at uniform speed

Hint:

Magnetostatic fields are produced by steady currents and permanent magnets. A time-varying electric field is associated with changing electromagnetic fields rather than magnetostatic ones.

Answer 1

The Correct Option is C

Magnetostatic fields are generated by steady currents (such as a DC current in a wire) or magnetic materials like permanent magnets. A time-varying electric field can induce a changing magnetic field, but it does not generate a magnetostatic field. The last option is correct as it represents an electric field, not a magnetic field source.