# We uses the energy of the electromagnetic field. Applications:

We have been familiar with the button above the door to an apartment or building since childhood. When you press it, the owner beeps – a melodic bell or a simple musical composition, warning about the appearance of the guest. So, that’s how does usual electric bell work. The electric bell has existed for two centuries, it uses the energy of the electromagnetic field.    Applications: They are used in fire or burglar alarms. It is used as alarms at some industrial plants because it is replaced by electronic sounders. It is used as a door bell.  The first electric bells appeared soon after the invention in 1823 by Englishman William Sturgen of electromagnets. The vibrating malleus was coined by Johann Philipp Wagner, and in 1839 John Mirand added a bell that determined the standard form of the bell. An electric bell contains an electromagnet, consisting of coils of insulated wire wound round iron rods. When an electric current flow through the coils, the rods become magnetic and attract a piece of iron attached to a clapper. The clapper hits the bell and makes it ring.  Principle of operation and the device of an electric bell on a direct current To create sound waves, small hammer strokes are used in the form of a steel ball located at the end of a spring plate, which strikes the bell with mechanical vibrations.This hammer is fixedly fixed to a movable armature, capable of moving relative to a fixed point of support.  Here are mounted:movable part of the composite magnetic core of the electromagnet; A spring with a device for adjusting the return force of the armature to its home position, which operates after the electric current circuit breaks; a movable contact that switches the supply of voltage to the coils of the electromagnet. Around the magnetic circuit are placed two electric coils with windings connected in series. When a direct current passes through the coils, a magnetic flux is created in the magnetic circuit, the value of which is summed up from the fluxes of each winding and many times higher than the values ??appearing in a single wire. The source of voltage / current in the circuit can be a certain galvanic cell (battery or battery), or a rectifier device, powered from a source of variable electrical energy. Magnetic materials can be divided up in soft (like iron) and hard (like steel) materials. The major difference between these two is that the soft magnetic material will lose its induced magnetism, whereas the hard material (ferromagnetic materials) will keep its magnetism, as soon as the external magnetic field is removed.  Fire alarm bells are divided into two categories: vibrating, and single-stroke. On a vibrating bell, the bell will ring continuously until the power is cut off. When power is supplied to a single-stroke bell, the bell will ring once and then stop. It will not ring again until power is turned off and on again.  I strongly believe that the invention has been a great alerting support for many people. For example, if a burglar was breaking into a house the electrical bell could be used as an alarm, making the burglar run away before stealing or destroying too much. But one of the negative side about this is that the burglar could run away when hearing the alarm and before the police can arrive. This would mean that the burglar will not be punished for the crimes as well as being able to do other criminal acts and putting more people in danger. However, the electric bell has had a positive impact on the social interactions between people, because it has made our lives easier (the doorbell) or safer (the burglary alarm).  In conclusion I want to say that the electric bell is one of the most important inventions in our daily life and plays an important role.