Electromagnets: “A Magnet Laboratory” 1959 PSSC; Francis Bitter, MIT; John Waymouth, Sylvania
Physical Science Study Committee Films (PSSC) playlist:
Physics & Physical Sciences playlist:
more at
‘Researchers in a lab at MIT in the late 1950’s show-off the power of electro-magnets, and in the process, accidentally set an experiment on fire… [Francis] Bitter is an important historical figure, whose degaussing techniques spared many an allied vessel from destruction by magnetic underwater mines during WWII. The generator shown was from Pittsbugh’s street car system, relocated to MIT for use in Bitter’s lab.’
Public domain film, slightly cropped to remove uneven edges, with the aspect ratio corrected, and one-pass brightness-contrast-color correction & mild video noise reduction applied.
The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).
Wikipedia license:
An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. The magnetic field disappears when the current is turned off. Electromagnets usually consist of insulated wire wound into a coil. A current through the wire creates a magnetic field which is concentrated in the hole in the center of the coil. The wire turns are often wound around a magnetic core made from a ferromagnetic or ferrimagnetic material such as iron; the magnetic core concentrates the magnetic flux and makes a more powerful magnet.
The main advantage of an electromagnet over a permanent magnet is that the magnetic field can be quickly changed by controlling the amount of electric current in the winding. However, unlike a permanent magnet that needs no power, an electromagnet requires a continuous supply of current to maintain the magnetic field.
Electromagnets are widely used as components of other electrical devices, such as motors, generators, relays, loudspeakers, hard disks, MRI machines, scientific instruments, and magnetic separation equipment. Electromagnets are also employed in industry for picking up and moving heavy iron objects such as scrap iron and steel…
Danish scientist Hans Christian Ørsted discovered in 1820 that electric currents create magnetic fields. British scientist William Sturgeon invented the electromagnet in 1824. His first electromagnet was a horseshoe-shaped piece of iron that was wrapped with about 18 turns of bare copper wire (insulated wire didn’t exist yet). The iron was varnished to insulate it from the windings. When a current was passed through the coil, the iron became magnetized and attracted other pieces of iron; when the current was stopped, it lost magnetization. Sturgeon displayed its power by showing that although it only weighed seven ounces (roughly 200 grams), it could lift nine pounds (roughly 4 kilos) when the current of a single-cell battery was applied. However, Sturgeon’s magnets were weak because the uninsulated wire he used could only be wrapped in a single spaced out layer around the core, limiting the number of turns.
Beginning in 1830, US scientist Joseph Henry systematically improved and popularized the electromagnet. By using wire insulated by silk thread, and inspired by Schweigger’s use of multiple turns of wire to make a galvanometer,[7] he was able to wind multiple layers of wire on cores, creating powerful magnets with thousands of turns of wire, including one that could support 2,063 lb (936 kg). The first major use for electromagnets was in telegraph sounders.
The magnetic domain theory of how ferromagnetic cores work was first proposed in 1906 by French physicist Pierre-Ernest Weiss, and the detailed modern quantum mechanical theory of ferromagnetism was worked out in the 1920s by Werner Heisenberg, Lev Landau, Felix Bloch and others…
The Physical Science Study Committee, usually abbreviated as PSSC, was inaugurated at a 1956 conference at MIT to review introductory physics education and to design, implement, and monitor improvements. It produced major new physics textbooks, instructional movies, and classroom laboratory materials, which were used by high schools around the world during the 1960s and 1970s and beyond…
By the 1964–1965 school year, about half the US students enrolled in high school physics (200,000 students, 5000 teachers) were reportedly using the PSSC course materials…
