19.2 Magnetic Forces and Currents | General Physics

Chad provides an introduction to Magnetic Fields and Forces related to Current-Carrying Wires in this lesson. He first introduces the formula for the magnetic force on a current-carrying wire: F=BIlsin(theta). It is demonstrated that the magnetic force is zero if the direction of the current is parallel or antiparallel to the magnetic field and at a maximum when it is perpendicular to the magnetic field. A right hand rule for determining the direction of the magnetic force is introduced and demonstrated and a practice problem is solved.

The formula for the magnetic field caused by a current-carrying wire is introduced next. It is explained that current-carrying wires not only can experience a force due to a magnetic field, but also generate their own magnetic field in a circular pattern around the wire that decreases in strength with distance from the wire. Another right hand rule is presented and demonstrated. A practice problem involving the determination of the magnetic force between parallel conductors is solved which incorporates the formulas for both the magnetic force felt by a current-carrying wire and the magnetic field generated by a current-carrying wire and the corresponding right hand rules.

The lesson is concluded with the presentation of the formula for the torque on a current-carrying loop. The torque is proportional to the number of turns of wire in the loop, the current in the loop, and the area of the loop, and is dependent upon how far the loop is from the normal to the magnetic field.

00:00 Lesson Introduction
00:44 Magnetic Force on a Current-Carrying Wire
03:25 Right Hand Rule #2
09:22 Magnetic Field Around a Current-Carrying Wire
09:56 Right Hand Rule #3
11:51 Parallel Conductors Magnetic Force Practice Problem
18:17 Torque on a Current-Carrying Loop

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