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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.
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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 = 1300.
electrotech@v-itc.ru

Answer the questions:
1. Why do electrons move along the circuit?
2. What does the strength of the magnetic field depend upon?
3. What is alternating current?
4. What is an alternating voltage?