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The difference in the electron and hole mobilities is responsible for the small negative Hall coefficient of intrisic semiconductors.

Refs: C.M.Hurd : Hall effect in metals and alloys

R.Asokamani :solid state physics

Busch& Schade; Solid state Physics

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What is Halls process an American student hall discover it?

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What is the basic difference between relaxation oscillator and RC oscillator?

The difference between an RC and LC is that the frequency - determining device in the RC oscillator is not a tank circuit. LC can operate with A or C biasing, while RC can only operate with A.


Why 6 db is a good attenuation?

6 dB is not good nor bad as an attenuation, if the context and the signal that is attenuated is not specified. As a rule of thumb, addition between dBs is multiplication between linear attenuation, thus since 3dB is a division of the power by two, 6 dB means a division of the power by 4. Just to give an idea: In free space, without obstacles and reflections, the power of a normal voice attenuates 6 dB in dry air in about 230 cm (assuming 180° directional sound emission of the mouth, that is reasonable). This is the combined action of intrinsic air attenuation (the sound ordered power is converted by traversing air in disordered oscillations of molecules: i.e. heath) that is very small (about 1 dB/km) and of the increase of the area where the power is distributed, that going farer and farer from the source is a sphere of greater and greater radius so that power decrease due to this last effect as the square power of distance from source. The humidity further reduces air intrinsic attenuation, but since the dominant phenomenon is the other, we can say that practically nothing changes. If music is considered, the situation is more complex. Music frequencies are much more extended than voice frequencies and attenuation of the material depends on frequency (while attenuation due to distance does not, as it is intuitive). High frequencies attenuates in air much more than low frequencies, for example 50 kHz attenuates about 0.9 dB/m in dry air for 180° directional sound emission. Thus attenuation also imply a small distortion of music due to its dependence on frequency. However this effect is not so relevant to be problematic when hearing music in concert halls, due both to the small distance and to the logarithmic sensitivity characteristic of out ears. Moreover in concert halls there are a lot of reflections that are exploited in the design of a good concert hall to concentrate the sound on the public, thus the real attenuation is much reduced by the fact that power diverging from the source is redirected towards the hall center by reflections. A problem to avoid in such a design is to exploit reflections from objects too far from the source or the hall. In this case reflections recover energy, but are also delayed with respect to the original sound, creating a bad echo effect. Light exhibit similar behavior, but much more evident due to the huge frequency extension of visible light.


How is multiple reflection useful for engineers?

Multiple reflection is useful for engineers in various fields, particularly in acoustics and optics. It allows for the optimization of designs such as concert halls and auditoriums, ensuring sound waves reflect in ways that enhance auditory experiences. In optical systems, it aids in the design of mirrors and lenses, improving efficiency and performance. Additionally, multiple reflection principles are applied in telecommunications to enhance signal transmission and reception in fiber optics.


What is a Assembly and what did they do?

An assembly is a gathering of individuals, often within a legislative or deliberative context, where members come together to discuss and make decisions on specific issues. In historical contexts, assemblies were crucial for enacting laws, debating policies, and representing the interests of various groups or communities. They played a significant role in shaping governance and ensuring that diverse voices were heard in the decision-making process. Examples include the Roman Senate, town halls, and modern legislative bodies like parliaments.