July 2012
Beginner
576 pages
9h 46m
English
Content preview from Complete Electronics Self-Teaching Guide with Projects
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Current Flow
1 Electrical and electronic devices work because of an electric current.
Question
What is an electric current?
Answer
An electric current is a flow of electric charge. The electric charge usually consists of negatively charged electrons. However, in semiconductors, there are also positive charge carriers called holes.
2 There are several methods that can be used to generate an electric current.
Question
Write at least three ways an electron flow (or current) can be generated.
Answer
The following is a list of the most common ways to generate current:
- Magnetically—This includes the induction of electrons in a wire rotating within a magnetic field. An example of this would be generators turned by water, wind, or steam, or the fan belt in a car.
- Chemically—This involves the electrochemical generation of electrons by reactions between chemicals and electrodes (as in batteries).
- Photovoltaic generation of electrons—This occurs when light strikes semiconductor crystals (as in solar cells).
Less common methods to generate an electric current include the following:
- Thermal generation—This uses temperature differences between thermocouple junctions. Thermal generation is used in generators on spacecrafts that are fueled by radioactive material.
- Electrochemical reaction—This occurs between hydrogen, oxygen, and electrodes (fuel cells).
- Piezoelectrical—This involves mechanical deformation of piezoelectric substances. For example, piezoelectric material in the ...
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