wjfox: Why is a semiconductor called a "semi" conductor, and not just a conductor?
GPT-4: Semiconductors are so named because their ability to conduct electricity falls somewhere between that of insulators, which do not conduct electricity well, and conductors, which do so freely.
In more technical terms, a semiconductor is a material that has an electrical conductivity value falling between that of a conductor, like copper, and an insulator, like glass. This middle ground is due to the presence of the so-called "energy band gap." In solid state physics, the band gap of a solid substance represents the energy difference (in electron volts) between the top of the valence band and the bottom of the conduction band in insulators and semiconductors. It's a sort of energy barrier that must be overcome for an electron to participate in electrical conduction.
In conductors, the valence and conduction bands overlap, meaning that there are always some electrons in the conduction band, which allows the material to conduct electric current. On the other hand, insulators have a very large band gap, which makes it very difficult for the electrons to jump from the valence to the conduction band, therefore inhibiting conductivity.
Semiconductors are unique because their band gap isn't as large as insulators but also isn't nonexistent like in conductors. It's a middle-ground scenario, hence the term "semi" conductor. This characteristic makes them very important in electronics because we can manipulate their conductivity. By adding impurities, a process called doping, we can control the number of free charges and therefore control the current, making semiconductors very useful for devices like transistors and diodes.
Re: Today I Learned
Posted: Tue Jun 20, 2023 6:56 pm
by raklian
My memories of watching "Finding Nemo" has been utterly destroyed.
While I already knew how it works, it was fascinating to watch it happen, especially at the end of the 2nd video below where it shows lightning being discharged through the wingtip.
Sometimes blood can look blue through our skin. Maybe you’ve heard that blood is blue in our veins because when headed back to the lungs, it lacks oxygen. But this is wrong; human blood is never blue. The bluish color of veins is only an optical illusion. Blue light does not penetrate as far into tissue as red light. If the blood vessel is sufficiently deep, your eyes see more blue than red reflected light due to the blood’s partial absorption of red wavelengths.
wjfox: I live in the UK and worry that the birds in my garden get too cold in winter. It's around -2°C in London today. How do they stay warm? Are their feathers good at holding heat? Do they cope better than humans with cold?
ChatGPT: Birds have several adaptations that help them stay warm in cold temperatures, like those you're experiencing in London. Here are the key ways birds cope with the cold:
Feather Insulation: Birds' feathers are excellent insulators. The outer feathers are waterproof and windproof, while the downy underlayer traps air, providing a layer of warm insulation. Birds can fluff up their feathers to trap even more air and increase insulation.
Behavioral Strategies: Birds often adopt specific behaviors to conserve heat. They might seek shelter in dense foliage, under eaves, or in birdhouses to avoid the wind and retain heat. Roosting in groups is another common behavior, as it reduces the amount of exposed surface area and shares warmth.
Shivering: Just like humans, birds can shiver to generate heat. This muscle activity increases their metabolic rate and helps to maintain body temperature.
Metabolic Rate: Many small birds have a high metabolic rate, which helps to generate body heat. However, this also means they need a constant supply of food to maintain their energy levels.
Tucking In: Birds often tuck their bills and one leg into their feathers to reduce heat loss. This posture minimizes exposed body parts.
Fat Reserves: Some birds build up fat reserves in the winter. This not only provides insulation but also serves as an energy source.
Birds are generally better adapted to cold temperatures than humans due to these natural mechanisms. Their feathers, in particular, are far more effective at insulation than most of the clothing materials used by humans. However, extreme cold can still be challenging for them, especially if it impacts their food supply. Helping birds during winter by providing food and water can be beneficial, especially when natural food sources are scarce due to snow or ice.
Re: Today I Learned
Posted: Mon Jan 01, 2024 8:03 am
by wjfox
TIL: Jupiter is the oldest planet in our Solar System and pre-dates the Earth by 50 million years.
Re: Today I Learned
Posted: Mon Apr 01, 2024 11:01 am
by wjfox
TIL: Sweden and Norway were once united and known as the United Kingdoms.
