Definition in electromagnetics: What is electromagnetism in the context of a current-carrying conductor?

Introduction / Context:
Electromagnetism connects electricity and magnetism. A foundational observation is that electric current flowing through a conductor produces a magnetic field encircling the wire. Recognizing this definition is essential for understanding motors, relays, inductors, and transmission lines.

Given Data / Assumptions:

• Steady or time-varying current through a straight conductor.
• Classical field behavior (no quantum effects required for the concept).
• Right-hand rule applies to field direction around the conductor.

Concept / Approach:

By Ampere’s law and experimental evidence, a current I establishes a circumferential magnetic field H around the conductor. The field intensity is proportional to current and inversely related to distance from the wire. This effect underlies inductance and is different from induction caused by changing magnetic fields (Faraday’s law).

Step-by-Step Solution:

Verification / Alternative check:

Using a compass near a current-carrying wire demonstrates deflection that reverses with current direction, confirming the magnetic field produced by the current.

Why Other Options Are Wrong:

• external voltage causing a magnetic field: Voltage alone does not create a magnetic field; current does.
• voltage caused by a magnetic field: That describes electromagnetic induction (emf) from changing flux, not the definition of electromagnetism here.
• current generated by an external magnetic field: That is induction again, requiring changing flux or motion.
• conversion of flux to heat: Not a definition; losses can cause heat but are not electromagnetism itself.

Common Pitfalls:

• Confusing electromagnetism (field due to current) with electromagnetic induction (emf due to changing magnetic field).
• Ignoring field orientation; use the right-hand rule to avoid sign mistakes.

Final Answer:

the magnetic field generated around a conductor when a current passes through it