<span> 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.</span>
A ferromagnetic material like iron, cobalt and nickel should be placed as a core in an electromagnet. These materials produce strong magnetic material when magnetic force acts. In an electromagnet, a conducting wire is wrapped around a core usually made of iron. When current flows in the wire, magnetic field is produced. The magnetic field causes the domains in the ferromagnetic materials to align in single direction and produce stronger magnetic field.
At 20 °C (68 °F), the speed of sound in air is about 343 metres per second (1,235 km/h; 1,125 ft/s; 767 mph; 667 kn), or a kilometre in 2.9 s or a mile in 4.7 s.
When the roller coaster moves down from the top of the hill, all of its stored potential energy is converted into kinetic energy to move it and when it goes back up the hill it turns kinetic into potential.
