Which law determines the magnetic field around a current-carrying wire?

Which law determines the magnetic field around a current-carrying wire?

• A. Gauss's law
• B. Ampere's law
• C. Coulomb's law
• D. Ohm's law

Answer: (B)

Ampere's law describes how a magnetic field is produced by an electric current. When current flows through a wire, it creates a magnetic field that forms concentric circles around the wire; its strength decreases with distance from the wire. The law is often written in its integral form: the line integral of the magnetic field around a closed path equals μ0 times the current enclosed. This directly links the magnetic field to the current that goes through the loop, which is why it’s the rule you use to determine the field around a current-carrying wire. The other laws describe different phenomena: Gauss's law concerns electric fields and flux, Coulomb's law deals with the force between charges, and Ohm's law relates voltage, current, and resistance.

Ampere's law describes how a magnetic field is produced by an electric current. When current flows through a wire, it creates a magnetic field that forms concentric circles around the wire; its strength decreases with distance from the wire. The law is often written in its integral form: the line integral of the magnetic field around a closed path equals μ0 times the current enclosed. This directly links the magnetic field to the current that goes through the loop, which is why it’s the rule you use to determine the field around a current-carrying wire. The other laws describe different phenomena: Gauss's law concerns electric fields and flux, Coulomb's law deals with the force between charges, and Ohm's law relates voltage, current, and resistance.