The three major improvements of the second Industrial Revolution were in the areas of energy and metal. It was based on oil, steel and electricity rather than coal and iron. The use of new materials made the second Industrial Revolution increase in size and technology, and mature more.ElectricityThe first dynamo, or electric generator, was developed in 1831. Its first applications were in communications. In 1837, two Englishmen had sent the first electric signals over a wire. In the 1870s, electricity was used to make the first electric motor, which would quickly replace the steam engine in industry. Electric motors were smaller, cleaner and cheaper than steam engines, and consequently they spread the Industrial Revolution throughout the manufacturing sector. The new motors could be used for many more things than steam - such as sewing machines and fans - and also light bulbs, which were invented in 1879 by Thomas Edison.Communications RevolutionAfter the first signal was sent over a wire, it was clear that electricity would produce a much better system of communication than ever before. The signals sent over a wire were developed into the telegraph, which the American Samuel Morse improved. Before long, Morse code, developed by the same Samuel Morse, was being used to send signals everywhere. The world was being strung with telegraph wires and undersea cables. The telephone, invented by Alexander Graham Bell in 1876, had promise of being an even greater technology. After that, in 1901, the first radio signals were sent across the Atlantic, heralding, to the inventor, a day when wires would not be needed to send signals.From iron to steelAt the same time as electricity was replacing steam, steel was replacing iron. New iron purifying processes were creating strong steel out of low-quality iron. Steel production subsequently increased dramatically, with falling prices. The cheap, hard steel made railway expansion boom.