Magnetic field viewing film is used to show stationary or (less often) slowly changing magnetic fields; it shows their location and direction. It is a translucent thin flexible sheet, coated with micro-capsules containing nickel flakes suspended in oil. When magnetic lines of force are parallel to the surface of the carrier sheet, the surfaces of the flakes are reflective, and appear bright. When lines of force are perpendicular to the sheet, the flakes are edge-on, and appear significantly darker. When the film is placed on a magnet's pole, the latter case applies, and most of the area of the pole appears dark.
If two cubical magnets are placed next to each other, poles facing up and down, and arranged to attract each other, their poles are dark, but a thin line between the poles is bright where the flakes reflect light.
Commonly-available film is green, although a translucent pale blue variety is also available.
Magnetic viewing film is sometimes used by hobbyists and electronics enthusiasts to examine commercial products. For example, iFixIt, a site that publishes "teardowns" (or deconstructions) of new technology, used magnetic-field viewing film in its teardown of the iPad 2 Smart Cover. The film revealed the magnet array inside the cover.
Famous quotes containing the words magnetic, field, viewing and/or film:
“We are in great haste to construct a magnetic telegraph from Maine to Texas; but Maine and Texas, it may be, have nothing important to communicate.”
—Henry David Thoreau (1817–1862)
“The woman ... turned her melancholy tone into a scolding one. She was not very young, and the wrinkles in her face were filled with drops of water which had fallen from her eyes, which, with the yellowness of her complexion, made a figure not unlike a field in the decline of the year, when the harvest is gathered in and a smart shower of rain has filled the furrows with water. Her voice was so shrill that they all jumped into the coach as fast as they could and drove from the door.”
—Sarah Fielding (1710–1768)
“Hereditary property sophisticates the mind, and the unfortunate victims to it ... swathed from their birth, seldom exert the locomotive faculty of body or mind; and, thus viewing every thing through one medium, and that a false one, they are unable to discern in what true merit and happiness consist.”
—Mary Wollstonecraft (1759–1797)
“Perhaps our eyes are merely a blank film which is taken from us after our deaths to be developed elsewhere and screened as our life story in some infernal cinema or despatched as microfilm into the sidereal void.”
—Jean Baudrillard (b. 1929)