Vacuum tube
is widely used in our daily life. In order to have a deep understanding of it,
Easybom has done a detailed study on the development process of vacuum tube.
People working in the electronic industry and interested in electronics can
learn from the following content summarizedEasybom.
The flow of current and electrons
Of course,
the vacuum tube was not experimented with several metal plates installed in a
vacuum glass bottle for no reason. The development of vacuum tube is related to
the invention king Edison.
There is a
small question: Do the current in circuit analysis and electrons share the same
flow direction? The answer is no, the direction of current and electron flow
are exactly opposite. In the past, scientists could not observe the direction
of electron flow, so they set a certain pole of the battery as the positive
electrode and its voltage was a positive voltage, and the current flowed from
the positive electrode to the negative electrode to form a closed loop. Because they unified statements and
practices, there has been no conflict for many years. But in modern time,
scientists used more sophisticated equipment to observe it, and then they
overturned the previous statement. “It comes to the conclusion that the
negative end of the battery is the place where the electrons
flow out from!”
Edison effect
As a user,
it is unnecessary for us to make clear which statement is true and we only need
to act according to the conclusion of the scientists. After the bulb invented
by Edison, he found that the filament of the light bulb he produced always
burned from the positive end, so he conducted an experiment. He added a small
metal plate into the bulb, then connected the metal plate to the electric meter
after lighting, and applied positive voltages and negative voltage
respectively, and finally observed the current situation.
With respect to the science at that time, metal plates in
a vacuum without connection could not generate current. But something strange
happened. Edison discovered that a certain substance (in fact, electrons) would
pass through the metal plate and jump from the negative pole of the battery to
the positive pole. This discovery provoked greater experimental motivation.
This phenomenon is called the “Edison effect”.This is also the first time
scientists have questioned the direction of current flow and the phenomenon of
free electrons flowing in space.
The birth of the vacuum tube
The reason
why metals can conduct electricity is that they have more free electrons, which
facilitate the flow of electrons. Therefore, electronic materials must be made
of materials with good conductivity. Electrons have another characteristic.
Negatively charged electrons are easily attracted by positive voltage, which is
the so-called repulsion homosexual and heterosexual attraction. We can also
know from the Edison effect that when a metal substance is heated, the free
electrons active in the periphery of protons are prone to dissociation and high
temperature leads to enhanced electron activity. At this time, if there is a
positive voltage in the space to strongly attract them, the dissociated
electrons will flow in space. Based on the knowledge that was already
understood at that time, J.A.Fleming produced the first diode vacuum tube in
1904. De Forest Lee improved the diode and produced the first triode in 1907.
Since the successful development of triode, the application of the vacuum tube
has begun to be realized.
