Magnetic Field Pattern Window - 21ENC00017 offers a thoughtfully designed, durable resource for hands-on learning. Magnetic Field Pattern Window _x000D_ A white frame with transparent window containing magnetic powder in a water based solution for showing magnetic field patterns. When a magnet is present the particles of iron inside become slightly magnetised, so they attract each other and cluster into the lines that show the magnetic field patterns. Includes a pair of small ferrite block magnets and a pair of plastic-cased bar magnets and teachers leaflet.