tag:techtv.mit.edu,:Array/232025520 2007-06-13 13:06:50 -0400 Doc Edgerton Films Piano hammer strikes wire 111 tag:techtv.mit.edu,:Array/232003500 2008-07-08 10:38:56 -0400 MIT Department of Physics Technical Services Group <p>Two large coils of wire ("Helmoholz coils") are connected to 125V DC power, and produce a uniform magnetic field between the coils. A separate coil is suspended with this field. Switching the polarity of the DC current in the inner coil causes it to rotate in opposite directions.</p><p>This principle is used by devices called <a href="http://en.wikipedia.org/wiki/Galvanometer">galvanometers</a> to measure electric current. </p> 47 tag:techtv.mit.edu,:Array/231981500 2008-06-26 13:51:08 -0400 MIT Department of Physics Technical Services Group <p>Two flexible wires are suspended vertically. The wires are conected in series or parallel to a 12V storage battery. When the wires are connected in series and power is applied they will repel each other; when they are connected in parallel they weill attract one another.</p><p>This effect is due to the magnetic fields created by the charge flowing through the wires. When the wires are in parallel, the currents in each are going in the same direction and thus attract. In series the currents are going in opposite directions and repel. </p> 50 tag:techtv.mit.edu,:Array/231960860 2009-01-21 14:43:14 -0500 MIT Department of Physics Technical Services Group A light bulb is connected in series with a coil of very fine copper wire and a DC power supply. The voltage is adjusted so that the bulb glows dimly. When the coil is immersed in liquid nitrogen the resistance of the wire decreases causing the current to increase and the bulb to glow brightly. 71 tag:techtv.mit.edu,:Array/231931760 2009-04-17 14:28:55 -0400 wrenow 10