Magnetic phenomena found

In 1822, French physicist  Arago  and Lussac found that when the current through the winding which has iron, which enables winding of iron magnetized. This is actually the principle of the electromagnet originally found. 1823, Sturgeon also did a similar experiment: magnetic traps is not on a U-shaped iron bar magnet bar 18 laps around the bare copper, copper wire and a voltaic battery when turned on, around the U copper coil type iron bars on the intensive magnetic field that is generated, thus making a U-shaped piece of iron rod into a "solenoid." magnetic plates than the permanent electromagnet can be big to put on times, you can pick up more than 20 times its weight of iron, and when the power is turned off, U-shaped iron bar on what iron also suck live, again become an ordinary iron bar.