If the silicon is heavily doped with arsenic, many free electrons are available and a high amount of current will flow. This is the same as saying that the material has a very low resistance. If only a few arsenic atoms are added, fewer electrons are available for current flow so the current level will be less with an external voltage. Such material has a much higher resistance.
As you can see, current flow in N-type semiconductor material is still by electrons. However, we can also dope the silicon with a material that has only three valence electrons.
This is illustrated in Figure 7 where the silicon is doped with boron B atoms. P-type semiconductor material where holes are the current carriers. The three valence electrons in the boron atom form co-valent bonds with adjacent silicon atoms.
However, one of the silicon atoms is missing an electron. This missing valence electron is referred to as a hole. A hole, therefore, is not an actual particle, but simply a vacancy in the valence shell of the crystal lattice structure that acts like a current carrier. This vacancy or hole has a positive charge. If an electron passes near the hole, it will be attracted and it will fill the hole, completing the co-valent bond.
Current flow in this type of semiconductor material is by way of holes. This type of semiconductor material is referred to as P-type material. P means positive, which refers to the charge of the hole. When an electrical voltage is applied to a piece of P-type semiconductor material, electrons flow into the material from the negative terminal of the voltage source and fill the holes. The positive charge of the external voltage source pulls electrons from the external orbits, creating new holes.
Thus, electrons move from hole-to-hole. Electrons still flow from negative-to-positive, but holes move from positive-to-negative as they are created by the external charge. In certain types of materials, particularly liquids and plasmas, current flow is a combination of both electrons and ions.
Figure 8 shows the simplified drawing of a voltage cell. All cells consist of two electrodes of different materials immersed in a chemical called an electrolyte. The chemical reaction that takes place separates the charges that are created. Electrons pile up on one electrode as it gives up positive ions creating the negative terminal while electrons are pulled from the other electrode creating the positive terminal.
Whenever you connect an external load to this battery, electrons flow from the negative plate, through the load, to the positive electrode. Inside the cell, electrons actually flow from positive-to-negative while positive ions move from negative-to-positive. So why do we continue to perpetuate the myth of conventional current flow CCF when we have known for a century that current in most electrical and electronic circuits is electron flow EF? I have been asking that question of my colleagues and others in industry and academic for years.
Despite the fact that electron flow is the reality, all engineering schools insist on teaching CCF. If you were in the armed services or came up through the ranks as a technician, chances are you learned and favor electron flow. The way you learned it in school is what you tend to use when you design, analyze, troubleshoot, or teach out in the real world.
As you may know, it doesn't really matter which current direction you use as circuit analysis and design works either way. In fact, this issue only affects DC that flows in only one direction. In alternating current, electrons flow in both directions, moving back and forth at the frequency of operation.
But if it truly does not matter which direction we assume, then why don't we default to the truth and end this nonsense once and for all?
If you ever want to start a lively conversation, maybe even an argument, try bringing up this subject in a group of technical people. You just may be surprised at the intensity of the feelings and the sanctimonious attitudes on both sides. I've done this numerous times and I am still amazed at the emotional response this issue generates.
My conclusion is that the concept of CCF will never be abandoned. It is somewhat akin to forcing us all to switch to the metric system of measurement using meters and Celsius rather than feet and Fahrenheit with which we are more familiar and comfortable. CCF will continue to be taught from now on. I have come to accept this whole thing as one of the stranger quirks of electronics. Early researchers of electricity first discovered the concept of voltage and polarity, then later went on to define current as the motion of charges.
The term voltage means the energy that makes current flow. Initially, voltages were created by static means such as friction or by lightening. Later, chemical cells and batteries were used to create a constant charge or voltage.
Mechanical generators were developed next. Charges refer to some kind of physical object that moves when it is subjected to the force of the voltage. Of course, back in the 18th century, those working on electrical projects didn't really know what the charges were. For all they knew, the charges could have been micro miniature purple cubes inside a wire or other conductor.
What they did know was that the voltage caused the charges to move. For purpose of analysis and discussion, they arbitrarily assumed that the charges were positive and flowed from positive-to-negative. This is a key point. They didn't really know the direction of current flow, so they theorized what was happening.
And, as it turned out, they guessed wrong. There is nothing wrong with being wrong as scientists are often hypothesizing one thing, then later finding that the truth is something else. The big mistake is that the incorrect hypothesis has been retained and taught as truth. In the late 19th century, it was finally determined that the charges being discussed were really electrons and the current was really electrons flowing from the negative terminal of a voltage source through the circuit to the positive side of the voltage source.
British physicist, Joseph J. There is a factor of a hundred at least between the force necessary to separate an electron from the electromagnetic field and separating a nucleon from the strong field.
In addition the positive bound protons are shielded electromagnetically by the electrons, one has first to remove the electrons to get at a proton. Thus it is easy to find the Kev energy to remove an electron around the atom than the MeV energy to free a proton.
Thus in the huge majority of materials it is the electrons that carry the negative charge, and positive charges one gets from the remaining ions, which are large and therefore smaller mobility large crossection for interactions.
The exception is the hydrogen atom, and we get protons to form a strong current in the particle accelerators. Single protons in matter cannot be enough in number to carry the currents a la electrons. They will tie up with an electron and find a pair to make a H2 molecule. When charges flow through a surface,they can be positive, negative, or both. The direction of conventional current is the direction positive charges flow. In a common conductor such as copper, the current is due to the motion of negatively charged electrons, so the direction of the current is opposite the direction of motion of the electrons.
On the other hand, for a beam of positively-charged protons in an accelerator, the current is in the same direction as the motion of the protons. In some cases— gases and electrolytes, for example—the current is the result of the flows of both positive and negative charges. Moving charges, whether positive or negative, are referred to as charge carriers. In a metal, for example, the charge carriers are electrons. The only way I know of to create proton flow would be via fusion.
I have read that fusing two He3 atoms together yields energy, Lithium, and a free proton; verses fusing deuterium and tritium isotopes of hydrogen , which produces energy, He, and a free neutron. I believe that a stream of protons would have a positive charge and could produce an electron current directly in something like a solar panel. This is why we need to go back to the moon It is common knowledge that electrons are mobile and therefore used in conductivity.
Electrons move freely within the structure of an atom but protons are bound in the nucleus and therefore immobile. Conductivity will therefore occur when electrons move from one atom to another and not protons due to their immobility.
We now learn particles are involved in conductivity and this particles will only aid in conductivity if they move. I think electrons are free to move but protons are bound with neutrons with higher force of attraction so electrons carry electric current but not protons. Its simple, electrons are on the outside of the nucleus of the atom. While protons and electrons can be transferred, they are on the inside of the nucleus and if they were transferred it would be considered a nuclear reaction.
Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
Create a free Team What is Teams? The electrons travel in a direction opposite the direction of the electric field, hence they will travel counterclockwise through the wire.
This is usually much higher than the forward voltage. As with forward voltage, a current will flow if the connected voltage exceeds this value. As we know from the i-v curve, the current through and voltage across a diode are interdependent. Once the voltage gets to about the forward voltage rating, though, large increases in current should still only mean a very small increase in voltage. The diodes will only move power loss from the regulator to the diodes themselves.
In this case it should be fine, but diodes do not drop a fixed voltage; the voltage drop varies depending on current in a non-linear fashion. While some like a diode or circuit breaker provides only the reversal voltage protection, others such as the protection ICs provide the reverse voltage, over current, and overvoltage protections.
LEDs emit light, only when they are forward biased. LEDs should be protected with a polarity protection diode if reverse bias voltages are likely.
Typical LEDs have about 2 Volts across them when lit but this varies from 1. Current is reversed when you hook a battery up to a component backwards or with the wrong polarity. It sends the current in the opposite direction it ought to be traveling to the circuit, which risks internal damage. Another cause of reverse current is accidental short circuits. Reverse Polarity Protection with a Schottky Diode An easy way to mitigate both of the above disadvantages is to use a Schottky diode instead of a normal diode.
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