Major Inventions and Discoveries Biology

Author: China Pictorial Publishing House
Publisher:
Publish Date: 1999-08-01
Features:
Fragment: Electric Bell
You might think the electric bell is simple, but in fact, it is a very complex device. How does an electric bell work? The working process of an electric bell mainly involves the repeated magnetization and demagnetization of an iron rod wrapped with a spiral wire coil. There are several coils inside the electric bell, with the central part being an iron rod called the "iron core." When the bell is pressed, the coils connect to the circuit, causing the "iron core" to become magnetized. As a result, the iron rod attracts the small hammer, which then strikes the small bell. When the hammer moves away, the circuit is disconnected, and the "iron core" loses its magnetism. However, when the hammer returns to its position due to the spring, the circuit is reconnected.
Magnetic Field
Danish physicist Hans Christian ?rsted (1777–1852) discovered that electric current produces a magnetic field around it. Later, scientists such as the French physicist André-Marie Ampère (1775–1836) conducted in-depth research on this phenomenon and artificially created magnetic fields and magnets. The British physicist Michael Faraday (1791–1867) demonstrated that a magnetic field can generate electric current. Thus, a new era began. By the late 19th century, people were already able to produce electricity on a large scale to meet demand. Faraday also experimentally proved the relationship between magnetism and electricity. Through his experiments, he placed a bar-shaped permanent magnet inside a cylinder wrapped with insulated wire coils. When he moved the magnet, he observed current flowing through the coils.