Capacitors, Inductors, and Transformers

A resistor presents a fixed value of resistance (opposition to current) that is independent of the type of voltage (dc or ac) applied to it. Capacitors and inductors are two types of electrical components classified as reactive, which means that their opposition to current depends on the type of voltage …

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Magnetism and Electromagnetic Devices

Magnetic Attraction and Repulsion

Magnetism and Electromagnetic Devices In this section, you will learn about basic magnetism and electromagnetism. Three important electromagnetic devices are introduced: the relay, the generator, and the motor. All of these devices are important in renewable energy systems. Relays are commonly used in many applications to switch current on and …

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Conductors, Insulators, and Semiconductors

Electricity consists of moving charge. When we think of the path for electricity, we think of wires most of the time. In metallic solids, electrons make up the charge that moves; however, the charge can also move through certain liquids and gases as well as space itself. In this section, …

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Series and Parallel Circuits

Four Examples of Parallel Circuits 1

Series and parallel circuits are two basic arrangements of the source and loads. Series and parallel circuits are often combined to form complex circuits that can be understood on the basis of simpler series and parallel arrangements.  Series Circuits A series connection is one with a single path. A series circuit has …

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Power and Watt’s Law

Watt Law

When there is current through a resistance, electrical energy is converted to heat or other forms of energy such as light. A common example of this is the incandescent light bulb that becomes too hot to touch when it has been on for a short time. The current through the …

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Resistance and Ohm’s Law

Cutaway View of a Carbon-Composition Resistor

With the exception of a special class of materials called superconductors, all materials have resistance, which is the opposition to current. Conductors are generally metallic materials with low resistance, whereas insulators are materials with high resistance. When there is current through a resistive material, heat is produced by the collisions …

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Electrical Current: Definition & Formula

Complete DC Circuit

The original idea of current was based on Benjamin Franklin’s belief that electricity was an unseen substance that moved from positive to negative. Conventional current is defined based on this original assumption of positive to negative. The original definition is widely used, although there is another definition of current called electron flow. Electrons move …

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Nuclear Energy Environmental Impact

The ITER Tokamak Fusion Reactor

Environmental Concerns The environmental concerns associated with nuclear reactors are very different than with fossil fuel–burning power plants. On the positive side, reactors do not emit greenhouse gases or other atmospheric pollutants. They also use significantly less fuel in terms of weight than coal-fired plants. Reactors for electricity production have …

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How Does Nuclear Energy Work

Diagram of a Pressurized Water Reactor

Nuclear Energy Nuclear energy derives its power from the enormous amount of stored binding energy in the nucleus of the atom, which is the energy that holds the nucleus of the atom together. By tapping this energy, a substance such as water is heated and converted to steam to drive …

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Environmental Impact of Fossil Fuels

The environmental effects of using fossil fuels can have a serious impact on the quality of life. The process of burning fossil fuels combines carbon in the fuel with oxygen in the air to form carbon dioxide (CO2) that is released to the atmosphere. This is true for all fossil …

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Types of Fossil Fuels

renewable energy sources in the united states

Fossil fuels are fuels formed from decaying plant and animal matter that was primarily formed over millions of years. Fossil fuels include coal, oil (petroleum), and natural gas. These fuels have been the primary energy source for over 200 years, but they will eventually have to be replaced by other sources …

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Circuit Breaker Terms and Definitions

Alternating current (AC): Current that reverses its direction of flow at regular intervals. Arc: A sustained discharge of electricity across a gap in a circuit or between electrodes, usually accompanied by the electrodes (contacts) being vaporized and/or melted by the extreme heat of the arc. Arc chute: A structure that contains arc dividers. …

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Circuit Breaker Racking

The four positions of LVPCBs as they are being inserted or removed from their cubicles include connected, test, disconnected, and removed (withdrawn).

The four positions circuit breaker must go through as they are being inserted or removed from their cubicles include connected, test, disconnected, and removed (withdrawn). See Figure 1. Connected-The breaker is connected to the bus, carries load current, and operates electrically (on electrically operated circuit breakers). Test-The primary stabs are …

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Arcing in Circuit Breaker

The zero crossover point is the point where current alternates and begins to change direction and the only point where an arc can be interrupted

Circuit breakers are switches designed to open and close circuits. They may be operated manually or automatically through the use of overcurrent protective devices (OCPDs). The automatic operation of a circuit breaker occurs when there is an abnormal condition such as an overcurrent or short circuit. For example, an overcurrent …

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Circuit Breaker Schematic Diagram


A schematic diagram is a drawing that shows electrical system circuitry with symbols that depict electrical devices and lines representing conductors. Only qualified persons should review schematic diagrams and perform work on circuit breakers. A qualified person is a person who has special knowledge, training, and experience in the installation, …

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Medium Voltage Circuit Breakers Operation


Low- and medium-voltage Vacuum circuit breakers are similar in construction and operation. One of the primary differences between them is that the OCPDs on LVPCBs are mounted on the circuit breakers, while medium-voltage circuit breakers use protective relays, which are typically mounted on the enclosure door. Medium-voltage circuit breakers have …

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