12.4 Current-Carrying Wires

Magnetic Fields

Since current-carrying wires are essentially just moving charges, they will also create a magnetic field. If you recall from Unit 3: Electric Circuits, current-carrying wires have negative charges, electrons, moving through them. This means that the magnetic fields are rings around the wire that are counterclockwise with the direction of the current. To find the direction of the magnetic field around a wire, you can simply imagine gripping the wire with your right hand, with your thumb pointing in the direction of the current. The magnetic field will be in the direction that your fingers curl in. This is the right-hand rule for current-carrying wires.

To find the magnetic field strength at a point next to the wire, you can simply use the equation below.

B=\frac{\mu_o I}{2 \pi r}

${B}$ is the strength of the magnetic field at a point near a wire
${\mu_o}$ is permeability of free space
${I}$ is the current through the wire
${r}$ is the distance of the point from the wire

Magnetic Fields

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