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Page 3 - Electronics Information Study Guide for the ASVAB

Electricity and Magnetism

Electricity is the energy produced from the motion of charged particles. Moving charged particles in turn create magnetic fields. Electricity and magnetism are intrinsically linked as the electromagnetic force.

Magnetic Field

Magnetic fields arise from the motion of charged particles. This occurs at the atomic scale with electrons surrounding nuclei and at a macroscopic scale with currents passing through circuits.

Conducting wires wrapped around a core, called electromagnets, create magnetic fields when a current passes through.

Inductor

Inductors, like capacitors and resistors, are passive electrical components. Inductors are made of a core that is usually magnetic with a conductive wire wrapped around it. Due to their composition, inductors oppose currents through the generation of a counter-electromotive force (EMF).

When a large current reaches an inductor, the inductor creates a proportionally large, opposing EMF that diminishes the current. The capacity with which the inductor does this is known as inductance. In AC circuits, inductors and capacitors form the overall impedance that acts analogously to the resistance in a DC circuit.

Transformer

Transformers are used to convert high voltage to low voltage or low voltage to high voltage. They consist of two inductors in close proximity that differ in the number of wrapped coils.

The difference in the number of coils results in the creation of a current with a different voltage in the nearby inductor by way of the varying magnetic field.

Motor and Generator Basics

A motor is a machine that transmutes electric energy into mechanical energy and a generator is a machine that transmutes mechanical energy to electric energy. These machines, like electricity and magnetism, are intrinsically linked to each other.

Inside of a motor is a looped wire connected to an AC or DC source with a commutator. Surrounding this looped wire is a stationary magnet that provides a uniform magnetic field. As the current passes through the wire, the magnetic field exerts a force and rotates the wire.

The mechanical rotation of a current conducting wire inside of a magnetic field serves as an electrical energy generator.

Other Study Tips

Study Ohm’s Law

Ohm’s law is an electrical law describing the relationship between voltage, amperage, and resistance. This law is written as such:

amperage = voltage/resistance (\(I = \frac{V}{R}\))

Having two of the measurements allows students to determine the missing piece, much as they might solve a simple math equation. This equation is used to determine a wide range of electrical measurements and needs and is a pivotal aspect of performing electrical services. When studying Ohm’s law, understand its applications and uses, and practice solving several different uses of the equation.

Study the Everyday Application of Electronic Concepts

Research different conductors and how well they perform. For instance, is metal an effective conductor of electricity? If so, what type of metal is best used to safely and effectively conduct electrical currents? From here, study insulators, how they work and what qualifies as an insulating property. Study different types of currents (direct, alternating) and circuits. Finally, study the different ways electricity is used, including technology for entertainment (e.g., radio, television) and technology to improve quality of life (e.g., general electricity, refrigerators).

Become Familiar with Electronic Symbols

Electrical shorthand is a learned language, so to speak, and may appear on the ASVAB. To study for this part of the Electronic Information section, study different electrical symbols, such as the symbols for resistors and transformers. This allows you to read various diagrams and equations regarding the electric field, as well as formulate your own equations and notes regarding electric actions and needs. To study appropriately, acquaint yourself with the different symbols and signifiers associated with electrical terminology.

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