CON 410 - Ch 17 Electrical

TRANSFORMING VOLTAGE AND CURRENT

- AC circuit the strength of the voltage and the polarity of the power source are always alternating, so rate and direction of current flow are always changing. - As current flow increases in the circuit, the magnetic field surrounding the conductor increases, and as current flow decreases, the field decreases. - Fluctuation in rate of current flow causes the magnetic field surrounding the energized conductor to expand and collapse

Classical Theory: Flow of Electrons

- Chemical elements are the fundamental materials that make up matter; they are the building blocks of the universe. - Hydrogen, oxygen, nitrogen, carbon, silicon, copper, iron, silver, and gold are among the more than 100 known elements - Atoms are the smallest unit of an element and are composed of several kinds of elementary particles, including protons, neutrons, and electrons.

ELECTRICAL CURRENT

- Magnetism is a force of attraction between ferromagnetic metals such as iron, nickel and cobalt and a force of repulsion between diamagnetic materials such as antimony and bismuth. - A magnet displays the properties of magnetism. - Magnets occur naturally such as the mineral magnetite. - Coiling insulated wire around an iron core and running current through the wire can produce an electromagnet.

Power

- Power is the rate at which work is accomplished; it is work or energy released divided by time. - The unit of power measurement that most individuals are likely familiar with is horsepower. - One horsepower is equivalent to 33 000 foot-pounds (ft-lb) of work per minute (550 ft-lb/s). - This is the equivalent of lifting a one-ton weight at a rate of 61⁄2 feet per minute. - One horsepower is equivalent to 746 watts power. The electrical unit of power is the watt.

Six primary ways of current

- Static electricity from friction - Thermoelectricity - Piezoelectricity - Electrochemistry - Photoelectricity - Magnetoelectricity

Electrical Current

- The movement of these infinitesimal masses is caused by the attraction of masses with unlike charges and the repulsion of masses that have like. - Masses that are oppositely charged, one positive and one negative, are attracted toward each other and masses that are similarly charged, either positive or both negative, have a repulsive force between them.

Modern Theory: Flow of Charged Particles

- electricity is tied to even smaller subatomic particles that possess either a positive or negative electromagnetic charge. - Not all subatomic particles have a charge - It is only the subatomic charged particles, those with an electromagnetic charge, that are associated with electricity.

Closed Circuit

- keep current flowing in an electrical conductor, there must be a difference in charge between the ends of the conductor. - A closed circuit is an uninterrupted path that allows a continuous flow of current through an electrical circuit.

Energy

- measurement of electrical energy consumption, the rate at which power is being consumed over a specified period of time in hours, results in watt-hours (Wh) of energy. - The standard billing for energy consumption is the kilowatt-hour (kWh), which is equivalent to 1000 watt-hours. - 1000 watt-hours (Wh) = one kilowatt hour (kWh)

Transformers

- transformer is an electrical device that transfers an alternating current and voltage from one circuit to another using the induction phenomenon - The device is used in a circuit to change voltage, current, phase, and other electrical characteristics.

Alternating Current

Alternating current (AC) is a continuous reversal of the direction of current flow such that at a point in time the current flow is in one direction and at another point in time it is in the reverse direction.

Amperage

Amperage is the rate of current flow and may be referred to as inductive flow.

Current Flow

Current flow is caused by electromotive force or voltage.

Direct Current

Direct current (DC) is current flow in one direction in an electrical circuit.

Mechanical

Electric motors drive pumps, saws, drills, blenders, lawn mowers, toys,

q=Pt

Electrical energy consumption (q) in watt-hours may be determined by the following expression, where power (P) is expressed in watts and time (t) in hours of operation: q = Pt

Heat

Electricity can heat the water Heat we wash with (a domestic water heater) and the water we use to make coffee (kettles) and cook our food (electric elements on stoves and ovens).

parallel circuits

Electricity has several paths it can follow from the energy source to ground.

What is electricity

Electricity is a form of energy tied to the existence of electrical charge and, as a result, is related to magnetism.

Phenomenon of Electricity

Electricity is a physical phenomenon tied to the behavior of positively and negatively charged elementary particles of an atom.

Producing Current Flow

Electricity is the flow of current through a conductor. Current must be forced to flow in a conductor by the presence of a charge. There are six primary ways that current can be forced to move through a conductor: - Static electricity from friction - Thermoelectricity - Piezoelectricity - Electrochemistry - Photoelectricity - Magnetoelectricity

Insulators

Insulators are materials that resist the flow of electricity.

Joules Law

On a direct current circuit, voltage (E) and amperage (I) are related to wattage through the DC power equation, also known as Joule's Law: P = EI

One Horsepower =

One horsepower is equivalent to 33 000 foot-pounds (ft-lb) of work per minute (550 ft-lb/s).

One horsepower is equivalent to

One horsepower is equivalent to 746 watts power. The electrical unit of power is the watt.

Resistance

Resistance (R) refers to the ability of a conductor to resist current flow and is measured in ohms.

Semiconductors

Semiconductors are materials that are neither good conductors nor good insulators

Energy Charge

This may be computed by the following equation, where energy consumption (q) is expressed in kilowatt-hours and unit cost of electricity ($/kWh) is expressed in dollars per kilowatt-hours: $energy = q · $/kWh

Fundamental Units of Electricity

Units used to describe electricity are: - Voltage - Amperage - Ohms

Voltage

Voltage (E), amperage (I), and resistance (Ω) in an active electrical circuit are related through Ohm's Law:

negative charge to positive charge

When opposite charges are placed across a conductor, negatively charged subatomic particles move from the negative charge to the positive charge.

Short Circuit

an inadvertent shortcut develops in a circuit that permits current flow through an unintentional path, a short circuit is created.

Nicked Wire

bottleneck is also created where a wire has been nicked, since part of the wire Overheats is removed

Capacitors

capacitor is composed of metal plates separated by air or a dielectric material such as paper, ceramic, or mica. Capacitors store electrical energy in an electrostatic field and release it later, much like your body stores and releases static electricity as you rub your feet across the carpet and touch a grounded object. capacitive effect on a series AC circuit causes the phase of the current to lead the phase of the voltage—that is, peak voltage lags peak current

chain reaction particle speed

chain-reaction effect of current flow occurs very rapidly, at about the speed of light (about 186 000 miles/s or 300 000 m/s).

Conductors

conductor carries electrical current without providing too much resistance to current flow.

Light

control electricity and can make it flow through a very fine wire (filament) in a light bulb, illuminating our rooms.

Ohm's Law

current through a conductor between two points is directly proportional to the potential difference across the two points. - Current flow is caused by electromotive force or voltage. - Amperage is the rate of current flow and may be referred to as inductive flow. - Resistance (R) refers to the ability of a conductor to resist current flow and is measured in ohms. - Voltage (E), amperage (I), and resistance (Ω) in an active electrical circuit are related through Ohm's Law: - E = IR

overload situation

design limitation is to restrict a 15-amp circuit to 80 percent of its rated capacity. This limits the circuit to 12 amps, maximum

Basic Electrical Circuit

electric circuit is a continuous path along which an electric current can flow.

simple current

flow of electric charge through a conductor is an electrical current or, simply current.

single subatomic particle speed

movement of a single subatomic particle is fairly slow, averaging about one-half inch per second.

Open Circuit

path of current flow is interrupted such as if the switch in a circuit is opened (turned off), an open circuit results

Crimped Pipe

pipe is crimped, it won't let as much water flow past the pipe at that point. That will reduce the total flow.

Series Circuits

series circuits on old Christmas tree lights. Through If one light bulb doesn't work, none of the lights will come on, because all the Every Bulb electricity has to flow through each light bulb in sequence

Single-Phase Alternating Current Power

single-phase (1Φ) alternating current distribution system refers to a system in which all the voltages of the supply vary in unison. A basic system typically has two conductors: one is neutral and the other carries current (the hot or live conductor).

Three-Phase Alternating Current Power

three-phase (3Φ) alternating current distribution system consists of three separate lines of single-phase power with each line out of phase by 120° (1⁄3 of a cycle).