In powerful electromagnets, the magnetic field exerts a force on each turn of the windings, due to the Lorentz force acting on the moving charges within the wire. The Lorentz force is perpendicular to both the axis of the wire and the magnetic field. It can be visualized as a pressure between the magnetic field lines, pushing them apart. It has two effects on an electromagnet's windings.The field lines within the axis of the coil exert a radial force on each turn of the windings, tending to push them outward in all directions. This causes a tensile stress in the wire. The leakage field lines between each turn of the coil exert a repulsive force between adjacent turns, tending to push them apart.
Amperes Law: Consider a wire carrying a current. The current
produces a magnetic field. Now consider a closed path. Amperes law states that the integral of B.dl around the
closed path is equal to mu_0*I, where I is the current enclosed within the closed path.
Amperes law is useful in calculating the magnetic field produced
by highly symmetric current distributions.
In the lecture, examples are given that show how to apply Amperes
law to calculate the magnetic field produced by a current carrying long, straight, cylindrical wire, a toroid,
and a solenoid.
Magnetic Field Produced By Current, Part 2
Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.