第 6 章，共 8 章12% 占考试比重
Electronics Information
Electronics Information tests knowledge of electrical principles, circuits, and components. Questions cover current, voltage, resistance, and common parts like resistors, capacitors, and diodes. This subtest is not part of the AFQT but is important for electronics and technical military careers. Understanding Ohm's law and the roles of basic components is central to a good score.
Basic Electrical Quantities
Electricity is described by a few core quantities, each with its own unit. Knowing these units and what they measure is fundamental.
Voltage in volts
Voltage is the electrical pressure that pushes current through a circuit, measured in volts.
Current in amperes
Current is the flow of electric charge, measured in amperes, often called amps.
Resistance in ohms
Resistance opposes the flow of current and is measured in ohms.
Power in watts
Electrical power is the rate of energy use, measured in watts and equal to voltage times current.
Ohm's Law and Circuit Calculations
Ohm's law ties voltage, current, and resistance together and is the most tested relationship in this subtest.
State Ohm's law
Voltage equals current times resistance, written as V equals I times R.
Solve for current
Rearrange to current equals voltage divided by resistance to find current.
Calculate power
Power equals voltage times current, giving the watts a device uses.
Apply the formulas
Substitute the known values, such as 12 volts and 4 ohms, to find the missing quantity like 3 amperes.
Circuit Types and Components
Circuits can be arranged in series or parallel, and each common component has a specific job. Recognizing them answers many questions.
Add series resistances
In a series circuit, resistances add directly, so two 10-ohm resistors total 20 ohms.
Understand parallel circuits
In a parallel circuit, the total resistance is less than the smallest single resistor.
Identify components
A resistor limits current, a capacitor stores charge, and a diode allows current in only one direction.
Know protective devices
A fuse breaks the circuit when current gets too high to prevent damage.
Conductors, Insulators, and Safety
Materials differ in how well they carry current, and safe handling of electricity depends on knowing which is which.
Recognize good conductors
Copper is an excellent conductor and is widely used in wiring.
Recognize insulators
Rubber, glass, and plastic resist current and protect against shock.
Understand AC and DC
Alternating current reverses direction periodically, while direct current flows steadily one way.
Know the transformer's role
A transformer steps AC voltage up or down for efficient power transfer.
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