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Показ дописів із міткою Відео уроки. Показати всі дописи
30 березня 2025
27 жовтня 2020
ALTERNATING CURRENT
ALTERNATING CURRENT
Current is defined as
increment of electrons. The unit for measuring current was named in honor of
A.M. Ampere, the French physicist. Thus it is called ampere. The symbol for
current is I. The electric current is a quantity of electrons flowing in a
circuit per second of time. The electrons move along the circuit because the e.
m. f. drives them. The current is directly proportional to the e. m. f.
A steam of
electrons in a circuit will develop a magnetic field around the conductor along
which the electrons are moving. The strength of the magnetic field depends upon
the current strength along the conductor. The direction of the field is
dependant upon the direction of the current.
If the
force causing the electron flow is indirect, the current is called direct (d.
c.). If the force changes its direction periodically the current is called alternative
(a. c.).
Alternating current is the current that changes direction periodically. The electrons leave one terminal of the power supply, flow out along the conductor, stop, and then flow back toward the same terminal. A voltage that caused current reverses its polarity periodically. This is properly called an alternating voltage. The power supply that provides the alternating voltage actually reverses the polarity of its terminals according to a fixed periodic pattern. A given terminal will be negative for a specific period of time and drive electrons out through the circuit. Then, the same terminal becomes positive and attracts electrons back from the circuit. This voltage source cannot be a battery. It must consist of some types of rotating machinery.
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