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Other factors that affect current flow
Ampers, volts, and resistance are present in every electric circuit to some extent. In addition, there are other factors that affect the flow of current in various types of circuits.
Inductive reactance, or inductance, is the electrical effect that tends to resist a change in current through a coiled conductor. In an alternating current or pulsating circute, inductance causes current to lag behinde voltage. Inductance is indicated in electrical equations by the letter L, and the unit of measurement is the henry.
Capacitive reactance, or capacitace, is the electrical effect that resists any change of voltage in the circuit, tending to store energy as voltage decreases or falls. Capacitance is indicated in electrical equations by the letter C, and the unit of measurement is the farad.
Impedance is the total opposition to the flow of alternating current in circuit; it is a function of resistance, capacitance, and inductance. The symbol for impendance is the letter Z, and the unit of measurement is the ohm.
Prefixing units to indicate quantity.
Certain Greek and Latin prefixes may be used with the names of the foregoing electrical units to indicate very small or very large quantities. Thus, microampere is a more convenient way of saying one one-millionth of an ampere; milliampere means one one-thousandth of an ampere; kilowatt is used to express one thousand watts; and megavolt is one million volts. The following comparison illustrates the convenience of such a system:
Quantity Prefix Example
.000001 micro microampere
.001 milli milliampere
1,000 kilo kilowatt
1,000,000 mega megavolt
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