LED arrangement for Xmas light
The world of engineering and technology keep advancing every day, but people tend not to know and understand the start, the basics and the genesis of this great adventure.
I keep on wandering, how do we come about all these electronics and garjets, I asked myself so many questions, is this part of the miracles and wonders of the old experienced by fore-fathers, are electronics made through magic and incantations, no, it should be by invoking spirits of dark powers. Source: Episode 1
Actually, some of these questions had been answered in the last episode of this post, hope I was able to reduce your curiosity about getting answers to those questions.
In this episode, I will continue to expatiate on the wonder works of semiconductor devices. I will start this episode by doing justice to a very important question that usually confuse some of my students on semiconductors. The last episode explained that semiconductors are neither insulators nor conductors but a material whose resistivity (10E-4 to 0.5 Ωm) lies in between insulators and conductors, then why don't we classified a semiconductor as a resistance material? That is the question. Answer shall be made available shortly, just stay with me.
Before we can make a worthy justice to the about question, we have to first understand the two physics terminologies "Resistivity and "Resistance".
FM Radio circuit arranged on a board for demonstration
What is a resistance?
Resistance is defined as the property of a material which oppose the flow of the current. The voltage applied across a conductor whose free electrons starts to move in a particular direction, when these motile electrons collapse with atoms or molecules and hence produce heat, these atoms or molecules alter their movements and oppose the flow of free electrons in the material. Resistance depends on the Length of material, cross-section area of a conductor and temperature of the matherial. It is ohms measured in ohms (Ω). It can be denoted mathematically by:
What is resistivity?
Resistivity is the property of a material which offers resistance to the flow of current through it, that is, It is a measure of how strongly a material opposes the flow of electric current. The resistivity is directly proportional to the temperature of the material, which means that, it depends only on the temperature of the matherial involved. and the S.I unit of resistivity is ohm-meter(Ωm). It presents as the resistance of a material with specific dimension. Resistivity can be expressed mathematically as:
Where l is the length of the conductor, a is the cross-section area of conductor,R –is the Resistance of the material and ρ is the electrical resistivity,
Having understand what the resistivity and the resistance of a material is, we can now proceed to solving the pressing question.
Justification to a pressing question on semiconductors.
Considering some properties of the following materials: A copper which is a conductor has a resistivity of 1.7 E-8Ωm, Germanium which is a semiconductor with a resistivity of 0.6Ωm, Glass is an insulator with resistivity of 9 E 11 Ωm and Nichrome is a resistance material with E-4Ωm resistivity. Germanium is a semiconductor with a resistivity quite higher compare to a copper material which is a conductor but It is quite lower compared with a glass which is an insulator. This justified that the resistivity of a semiconductor lies in between insulator and conductors. However to consider a semiconductor as a resistance material based on this fact, we will be very wrong because even Nichrome as an example which is considered as one of the highest resistance material has it resistivity much lower than that of a germanium. Therefore, germanium can not considered or grouped as a conductor or insulator or a resistance material.
It should be noted that resistivity of a material alone is not enough to consider the material as a semiconductor or not. As an illustration, if an alloy is prepared whose resistivity falls within the range of that of semiconductors, we can not consider the alloy as a semiconductor just because it has the required resistivity.
The following unique properties distinguish semiconductors from insulators, resistance materials and conductors: Semiconductor resistance decreases with increase in temperature, and it increases with decrease in temperature. Also, the resistivity of a semiconductor must be less than that of an insulator but most be more than that of a conductor and Current conductivity property of a semiconductor increases significantly by doping with a suitable metallic impurities such as arsenic and gallium etc.
Troubleshooting an electronic board to detect fault
This serves the end of this episode, hope I was able to do justice to the pressing question on semiconductor.
The question was given to some of my students as an assignment, it nearly pull off their legs from a ladder.
Do not miss the next episode.
Thanks for your time.