Origin of magnetic fields A magnetic field exists around which of the following?

Introduction / Context:
Magnetism and electricity are fundamentally linked. Ampère’s law and Maxwell’s equations show that magnetic fields are produced by moving charges (currents) and by changing electric fields. This question focuses on the most direct, classical source: electric currents.

Given Data / Assumptions:

• Quasi-static conditions; displacement current contribution not emphasized here.
• Material (iron, copper, etc.) does not spontaneously create a magnetic field without current or magnetization.
• Permanent magnets originate from microscopic bound currents (electron spins/orbits), effectively moving charges.

Concept / Approach:

Magnetic field H (or B) arises from conduction currents (moving charges) and equivalent bound currents associated with magnetization. A stationary point charge produces only an electric field, no magnetic field. Materials like iron or copper can guide or respond to magnetic fields, but without current or magnetization there is no field generated.

Step-by-Step Solution:

Verification / Alternative check:

Right-hand rule around a current-carrying wire visualizes circular magnetic field lines, confirming the role of moving charges.

Why Other Options Are Wrong:

(b) Static charges produce only electric fields; (c) and (d) improperly attribute field generation to a material without current; (e) permanent magnets arise from microscopic currents—still “moving charges.”

Common Pitfalls:

Assuming magnetic materials always produce fields; confusing field generation with field conduction or concentration via high permeability.

Final Answer:

Moving charges (electric currents)