Sending Magnetic Signals Through Your Body

Magnetic fields provide a new way to communicate wirelessly

A new technique could pave the way for ultra low power and high-security wireless communication systems

This is a prototype of the magnetic field human body communication, developed in Mercier's Energy-Efficient Microsystems Lab at UC San Diego, consists of magnetic-field-generating coils wrapped around three parts of the body, including the head, arm and leg. Credit: Jacobs School of Engineering, UC San Diego
This is a prototype of the magnetic field human body communication, developed in Mercier’s Energy-Efficient Microsystems Lab at UC San Diego, consists of magnetic-field-generating coils wrapped around three parts of the body, including the head, arm and leg.
Credit: Jacobs School of Engineering, UC San Diego

[dropcap]E[/dropcap]lectrical engineers at the University of California, San Diego demonstrated a new wireless communication technique that works by sending magnetic signals through the human body. The new technology could offer a lower power and more secure way to communicate information between wearable electronic devices, providing an improved alternative to existing wireless communication systems, researchers said. They presented their findings Aug. 26 at the 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society in Milan, Italy.

While this work is still a proof-of-concept demonstration, researchers envision developing it into an ultra low power wireless system that can easily transmit information around the human body. An application of this technology would be a wireless sensor network for full-body health monitoring.

“In the future, people are going to be wearing more electronics, such as smart watches, fitness trackers and health monitors. All of these devices will need to communicate information with each other. Currently, these devices transmit information using Bluetooth radios, which use a lot of power to communicate. We’re trying to find new ways to communicate information around the human body that use much less power,” said Patrick Mercier, a professor in the Department of Electrical and Computer Engineering at UC San Diego who led the study. Mercier also serves as the co-director of the UC San Diego Center for Wearable Sensors.

Communicating magnetic signals through the human body

The new study presents a solution to some of the main barriers of other wireless communication systems: in order to reduce power consumption when transmitting and receiving information, wireless systems need to send signals that can easily travel from one side of the human body to another. Bluetooth technology uses electromagnetic radiation to transmit data, however these radio signals do not easily pass through the human body and therefore require a power boost to help overcome this signal obstruction, or “path loss.”

In this study, electrical engineers demonstrated a technique called magnetic field human body communication, which uses the body as a vehicle to deliver magnetic energy between electronic devices. An advantage of this system is that magnetic fields are able to pass freely through biological tissues, so signals are communicated with much lower path losses and potentially, much lower power consumption. In their experiments, researchers demonstrated that the magnetic communication link works well on the body, but they did not test the technique’s power consumption. Researchers showed that the path losses associated with magnetic field human body communication are upwards of 10 million times lower than those associated with Bluetooth radios.

“This technique, to our knowledge, achieves the lowest path losses out of any wireless human body communication system that’s been demonstrated so far. This technique will allow us to build much lower power wearable devices,” said Mercier.

Lower power consumption also leads to longer battery life. “A problem with wearable devices like smart watches is that they have short operating times because they are limited to using small batteries. With this magnetic field human body communication system, we hope to significantly reduce power consumption as well as how frequently users need to recharge their devices,” said Jiwoong Park, a Ph.D student in Mercier’s Energy-Efficient Microsystems Lab at the UC San Diego Jacobs School of Engineering and first author of the study.

The researchers also pointed out that this technique does not pose any serious health risks. Since this technique is intended for applications in ultra low power communication systems, the transmitting power of the magnetic signals sent through the body is expected to be many times lower than that of MRI scanners and wireless implant devices.

Another potential advantage of magnetic field human body communication is that it could offer more security than Bluetooth networks. Because Bluetooth radio communicates data over the air, anyone standing within 30 feet can potentially eavesdrop on that communication link. On the other hand, magnetic field human body communication employs the human body as a communication medium, making the communication link less vulnerable to eavesdropping. With this technique, researchers demonstrated that magnetic communication is strong on the body but dramatically decreases off the body. To put this in the context of a personal full-body wireless communication network, information would neither be radiated off the body nor be transmitted from one person to another.

“Increased privacy is desirable when you’re using your wearable devices to transmit information about your health,” said Park.

Demonstrating magnetic communication with a proof-of-concept prototype

The researchers built a prototype to demonstrate the magnetic field human body communication technique. The prototype consists of copper wires insulated with PVC tubes. On one end, the copper wires are hooked up to an external analyzer and on the other end, the wires are wrapped in coils around three areas of the body: the head, arms and legs. These coils serve as sources for magnetic fields and are able to send magnetic signals from one part of the body to another using the body as a guide. With this prototype, researchers were able to demonstrate and measure low path loss communication from arm to arm, from arm to head, and from arm to leg.

Researchers noted that a limitation of this technique is that magnetic fields require circular geometries in order to propagate through the human body. Devices like smart watches, headbands and belts will all work well using magnetic field human body communication, but not a small patch that is stuck on the chest and used to measure heart rate, for example. As long as the wearable application can wrap around a part of the body, it should work just fine with this technique, researchers explained.

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The above post is reprinted from materials provided by University of California – San Diego. Note: Materials may be edited for content and length.

What is the Difference Between a Disc and a Disk?

In computers, disks are used for the storage of data.
In computers, disks are used for the storage of data.

Origin of Disc and Disk

For the most part, the words “disc” and “disk” can be used interchangeably to describe flat, rounded objects. The British tend to prefer “disc,” and Americans generally use “disk” as their default spelling. In some cases, the spelling with a “k” at the end is based on Germanic origins, and the spelling with a “c” at the end is based on Greek or Latin origins. The use of “disc” or “disk,” however, is often simply a matter of preference within a particular field of use. No matter the field or the typical spelling for a particular object, it is not unusual to see the other spelling used, even by respected sources.

The word “disk” entered the popular vernacular first, sometime during the 17th century. By the 18th century, however, there was a movement toward incorporating Latin roots whenever possible. The Latin word discus led to the use of “disc” to refer to thin, circular objects.

In Real World

Discs or disks appear in fields such as computers, media, science, anatomy and automotive mechanics. Some of these fields primarily use one spelling, and others use both, depending on the specific object. In many fields, the spellings can be used interchangeably.

Compact discs can store data.
Compact discs can store data.

In computers and media, “discs” or “disks” typically refer to storage devices for data, music and videos. Phonographic records were also known as discs, and people who played records on radio stations were called disc jockeys. When optical storage devices were introduced, this spelling carried over into compact discs (CDs) and digital versatile discs (DVDs). Magnetic storage devices often use the spelling with a “k” as seen in floppy disks and computer hard disks.

Anatomical objects typically use the “disc” spelling. For example, a healthcare professional might refer to a “herniated disc” when a patient has a certain injury to the fibrocartilage between vertebrae in the spine. Other discs in the human body include optic discs in the eyes and placental discs in females.

"Disc" is commonly used in the context of the spine and spinal injuries like disc herniation.
“Disc” is commonly used in the context of the spine and spinal injuries like disc herniation.

In automotive mechanics, a disc brake is a device that uses friction against a circular metal plate to slow or stop the vehicle’s wheel.

In astronomy, the shape of a galaxy might be described as a disc. A ring of debris orbiting an object such as a star, on the other hand, typically is referred to as a debris disk.





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What is 4G Mobile Technology?

Fourth Generation (4G) mobile technology is a set of standards for providing broadband Internet access to devices like cellphones and tablets. Though it first became available in the US in 2009, no specific technologies were officially designated as 4G until 2011. Despite this, many devices were labeled as “4G” even though they did not meet the International Telecommunication Union’s (ITU) standards for the technology. The main difference between it and previous standards is a big increase in data transfer speeds and the types of media people can access with it.


There are also a number of technical specifications, including things like the wireless standard, radio interface, and frequency spectrum used. As of 2011, there were only two technologies officially designated as 4G mobile: LTE-Advanced and WiMax Release 2. Though devices using these technologies can theoretically reach the data speeds and functionality requirements set out by the ITU, the actual function varies according to the network coverage, infrastructure, and location.


Other Versions

Former versions of LTE and WiMax, and another technology called HSPA+, are also commonly referred to as 4G; despite the name, none actually meet the standards set out in IMT-A. The technologies were marketed so often as “4G” that the ITU allowed them to claim the designation. Most major carriers in the US work with at least one of these standards, with some supporting both. Generally speaking, LTE services are faster than WiMax, but WiMax can often support a farther-ranging signal than LTE, meaning that a user could conceivably use the mobile device farther away from a hotspot. Additionally, LTE is primarily used for cellphones and similar mobile devices, while WiMax is sometimes used to provide at-home Internet connections.

As Compared to 3G

The main difference between 4G mobile technology and the previous standard, 3G technology, in terms of end usage is the data transfer speeds provided. This means that users can access much more sophisticated data that requires a lot of bandwidth very quickly. Depending on the service provider, however, 4G mobile devices may be limited to specific zones for making phone calls that are generally smaller than the areas covered by 3G. This means that people trying to make a call would have their call dropped if they went outside the covered area. Some 4G phones also have much shorter battery life than most 3G phones.


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What Is Electrical Conductivity?

Power lines are made of conducting materials.
Power lines are made of conducting materials.

Electrical conductivity (EC) is a property that is used to describe how well materials allow electrons to flow. It is determined using experiments and math equations. Conductivity is the reciprocal of resistivity, meaning the higher the conductivity, the lower the resistivity. A conductor is a material that has a high electrical conductivity, and an insulator is a material that has a high electrical resistivity. Both properties depend on the temperature and purity of materials.

Temperature dependence of electrical conductivity follows a general pattern. Metal is a conductor, and it has lower conductivity at higher temperatures. Glass is an insulator and shows higher conductivity at higher temperatures.

At very high temperatures, conductors behave like insulators, and insulators behave like conductors. This behavior of insulators and conductors is explained by the free electron model. In this model, conductors clearly show the ability to free electrons, and when a current, or electric force, is applied, the force can easily push around the extra electrons.

Soil is a mixture of minerals, salts and organic materials. It has a special electrical conductivity called soil electrical conductivity, which measures the amount of salt that is in a soil sample, which is called its salinity. The process can also measure other soil properties where salinity is low enough. These properties are related to the influence that purity has on EC data.

EC data of a soil sample can determine how much impurity is in the soil. Soil impurities are water, air and minerals. Each impurity influences the data differently, but a practiced soil scientist can determine this information from the gathered data. In general, more impurities lower the EC, with the exception of minerals that increase EC. Impurities also can explain the use of pure copper in electrical wiring.

Metals are often made of alloys, a mixture of two or more elements. This is not useful for conducting electricity. The metals in alloys are not the same elements and electrons cannot flow easily between different elements. Pure metals, such as copper wire, have high electricalconductivity. This applies only to solid metals because air pockets can lower the electricalconductivity of materials.

Materials that are not metals usually make good insulators. The best insulators are materials that naturally have air pockets in them, such as rubber. The air pockets are like impurities and disrupt the flow of electrons. Gases, such as air, are the best natural insulators. Modern chemistry has mastered insulators, creating materials that have thousands of times more resistivity than air.


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What Is Electrical Resistivity?

Ohm's Law can be used to find the electrical resistance applied to a circuit by resistors.
Ohm’s Law can be used to find the electrical resistance applied to a circuit by resistors.

Electrical resistivity is the characteristic of a conductor, a semiconductor, or an insulator that limits the amount of current flow. It is determined by the atomic or molecular properties that may either allow or impede the flow of free electrons through the material. Electrical resistivity is almost the same as electrical resistance with the slight difference in the way electrical resistivity may refer to resistance of a specific length of a material. For instance, a basic unit of resistivity could refer to the amount of resistance per unit length of a copper cable.

Ohm’s law provides the relationship between the electrical resistance (R), the voltage (V), and the current flow in amperes (A). Resistance is the ratio of the voltage to the current. For the same voltage, a higher current is a result of a lower resistance. An electrical fuse is meant to have a very low voltage drop when placed in series with an electrical load. If the load is 9.999 ohms and the fuse has a resistance of 0.001 ohms, a 10-volt (V) supply voltage will produce a current of 1 A and the voltage across the fuse is negligible at 0.001 V.

Electrical resistivity tomography is an imaging tool that is able to present a three-dimensional profile of embedded materials. This is accomplished by using embedded electrodes and direct current (DC) to create a two-dimensional image. By using perpendicular image planes, it is possible to have an idea of the three-dimensional layout.

Various elements with notable electric resistivity have different uses in electrical applications. Silver and gold are very low-electrical resistivity elements that are used for special applications such as microbonding used in the semiconductor industry. Copper is the chosen commercial conductor sure to its acceptable electrical resistivity and relatively low price. Carbon is a low-cost material of choice for medium to high resistance resulting in huge varieties of carbon resistance in the market. The high stability of tungsten in relatively high temperatures makes it a common choice for incandescent and filament applications such as light bulbs, wire-wound variable resistors, and electric heaters.

Contact electrical resistance is usually very low when the conductive surfaces are not contaminated. In the case of relay contacts, the pressure that temporarily joins them determines how low the resistance will drop when the contact is closed. If the pressure is not enough and the current is high, it is possible for the contact to form plasma that can melt the contact. The spark generated due to repeated closures shortens the relay lifespan. In most cases, it is a good idea to use electronic DC switches such as the silicon-controlled rectifier (SCR) or use electronic alternating current (AC) switches like the three-terminal AC (TRIAC) switch.


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What Is a Power Supply?

Solar panels are a type of power supply.
Solar panels are a type of power supply.

A power supply is a device that takes an incoming electrical current and amplifies it to levels required by various devices. In many instances, this type of device is also implemented to take the incoming electricity and deliver it across many other electronic devices, often at different preset levels. This device allows manufacturers to create electronics and machinery that can handle many different tasks from a single source of power, without the need for various adapters and additional hardware. Within other devices, a power supply is used to transform various types of power into a compatible format to be stored, like solar energy to electrical energy.

Perhaps the most common use of this type of device is within computer systems. As electricity enters the power supply, it is momentarily stored and then distributed to numerous functions throughout the system, allowing the motherboard, hard drive, and other various devices to receive electricity in order to function. Each one of these items requires a separate voltage, and it is delivered through specialized connectors that attach in a certain manner. For example, motherboards require either a 20-pin or a 24-pin power supply, and they are not interchangeable without the purchase of an additional adapter.

Modern vehicles also require a type of power supply in order to function, and it is referred to as an alternator. Although the wiring and design may be different, it essentially works in the exact same manner by taking incoming power and delivering it throughout the vehicle at the necessary levels. Alternators can be found on everything from lawn mowers to sea craft and industrial equipment, and without them, the devices would be rendered useless.

automobile alternator - Winged Post 0419515
An automobile engine’s alternator essentially serves as an electric generator.

Another common type of power supply can be found on windmills and solar panels, and its primary function is to convert various types of energy into electricity so that it can be stored and distributed across a grid. This is referred to as a generator, and it is often a free-standing object that is installed between the power source and the storage unit. Home and commercial generators, used during power outages, also work off of this same premise by transforming petroleum products into electrical energy by means of an engine. Many types of industrial tools also implement a type of generator. Other common types of power supplies are used within circuit breakers, battery-powered items and transformers.


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What Is Diode Voltage Drop?



A diode is a common semiconductor device used in many different types of electronic circuits. When an electrical signal passes through a diode, the diode consumes a small amount of the signal’s voltage in its operation. The difference between the voltage of the signal entering the diode and the voltage of the signal exiting the diode is the diode voltage drop. Although a diode voltage drop can refer to either the diode’s forward or reverse voltage drop, it typically describes the forward voltage drop.

The construction of a diode involves joining an anode and a cathode, two pieces of material with different electrical charges. The anode is positively charged and the cathode is negatively charged. At the point where these two different materials meet, called the junction, the two different opposing charges effectively cancel each other out. This area without a charge is the diode’s depletion layer, which forms an insulating layer within the diode between the anode and cathode.

When an electrical signal enters a diode’s cathode, the additional negative force increases the width of the depletion layer as it reacts with the positively charged anode. The wider depletion layer will block the signal from passing through the diode and consume all of the voltage in the process. For example, if 5 volts enter the diode, the diode voltage drop will also be 5 volts. A diode in this state is reverse biased, and the voltage drop is the diode’s reverse voltage drop.

An electrical signal entering a diode’s anode creates a different set of conditions within the diode. The negatively charged signal will bridge across the anode, meet the cathode, and pass through the diode, continuing on to the rest of the circuit. In the process, a relatively small amount of thevoltage is lost overcoming the anode’s positive charge. For a typical silicon diode, the voltage lost is approximately 0.7 volts. A diode in this state is forward biased, and the voltage drop is the diode’s forward voltage drop.

The difference between the forward and reverse states in a diode permits them to block a signal in one direction by dropping 100% of the voltage but allowing it to pass in the other by only dropping a small amount. As most diodes have a reverse voltage drop of 100%, the assumption is that the term “diode voltage drop” refers to the forward voltage drop; however, this is not always the case.

Specialty diodes exist that do not drop 100% of the reverse voltage, such as varicap or varactor diodes. In these diodes, the charges of the cathodes and anodes are not even across their widths. As a result, these diodes can allow part of the signal entering the cathode to pass through the diodes even though they are in a reverse biased state. When describing the voltage drop in these types of diodes, it is important to differentiate between the forward and reverse voltage drops.


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What Is Voltage Drop?


A multimeter can be used to measure voltage drop.
A multimeter can be used to measure voltage drop.

Voltage drop is a term used to describe any reduction in the supply voltage in a complete electrical circuit. The term may be used to describe a voltage loss across a specific component in the circuit, the voltage loss measured across the entire circuit, or as a broad description of the phenomenon of voltage loss in a circuit in general. All electrical circuits, no matter how simple, present a certain amount of resistance to the flow of electrical current through them. This resistance effectively makes the electrical current work harder, and thus absorbs energy. This expenditure of energy is what causes the reduction in voltage described by the term voltage drop.

For example, a simple circuit can be made up of a 9-volt battery attached to a simple flash light bulb with a small switch. If one were to measure the voltage across the batteries terminals with the switch open, the multimeter reading would be approximately 9 volts. If one were to close the switch and illuminate the bulb, that reading would drop by approximately 1.5 volts. That reduction in voltage is what is known as a voltage drop, and it comes about as the result of the work the battery has to do to illuminate the bulb. Each and every component in a circuit, including the wiring, offers a certain amount of resistance to the flow of electrical current and will cause an associated voltage drop.

In applications that are extremely supply voltage sensitive, such as electronic devices, these voltage losses have to be carefully calculated and the supply voltage adjusted to make provision for them. A 12 volt direct current (DC) power supply, for instance, will typically produce an output of 13.8 volts to accommodate this voltage drop phenomenon. In applications that require very long cable runs, it is common practice to uses fairly heavy cables that present less resistance to the flow of electric current in an attempt to minimize the effects of voltage losses. The total potential loss of voltage in any circuit thus needs to be carefully calculated during the design and specification phase of a project to ensure that the final result meets all requirements.

Any voltage loss in a circuit can, fortunately, be calculated with great accuracy using a voltage drop formula. This makes it possible to achieve consistent and predictable results at the end of an installation. These calculations will differ according to the type of circuit, voltage supply, and components involved and can be extremely complex, often requiring the use of a voltage drop calculator. They do, however, take the guess work of accurately adjusting power supply specifications to accommodate circuit resistance.


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What Is Electrical Energy?

On a diesel-electric locomotive, a diesel engine provides power to an electric traction motor that turns the unit's wheels.
On a diesel-electric locomotive, a diesel engine provides power to an electric traction motor that turns the unit’s wheels.

Electrical energy results from the movement of an electrical charge, and is commonly referred to as simply “electricity.” Ultimately, it has its origin in the electromagnetic force: one of the four fundamental forces of nature and the one that is responsible for the behavior of electrically charged objects. Electrical energy is the result of the interaction of subatomic particles with this force. Electricity manifests itself in natural phenomena such as lightning and is essential to life at a fundamental level. The ability of humans to generate, transmit and store electricity is crucial to modern industry, technology and, in most countries, domestic life.

The Origin of Electrical Energy

There are two types of electrical charge, called positive and negative. If two electrically charged objects are brought close to one another, they will experience a force. If the charges are the same — both positive or both negative — the force will act to push the objects away from one another. If they have different charges, they will attract one another. This repulsion or attraction is known as the electromagnetic force, and it can be harnessed to create a flow of electrical energy.

Atoms consist of a nucleus containing positively charged protons, with negatively charged electrons orbiting around it. Protons normally stay put in the nucleus, but electrons can move from atom to atom, allowing them to flow through materials, such as metals, that conduct electricity. A place with an excess of electrons over protons will have a negative charge; a place with a deficit will have a positive charge. Since opposite charges attract one another, electrons will flow from a negatively charged area to a positively charged one if allowed to do so, creating an electric current.

Using Electrical Energy

Electricity is useful both in itself and as a means of transferring energy over long distances. It is essential to various industrial processes, telecommunications and the Internet, computers, televisions and many other devices in common use. It can also be converted into other forms of energy for use in a variety of other applications.

When an electric current flows through a conductor, it generates a certain amount of heat. The amount generated depends on how well the material conducts electricity. A good conductor, such as copper, produces very little. For this reason, copper wires and cables are commonly used to transmit electricity: when heat is produced, energy is lost, so a good conductor minimizes energy loss. Materials that conduct electricity less well produce more heat, so they tend to be used in electric heaters, cookers and ovens, for example.

Electrical energy can also be converted into light. Early arc lights depended on an electrical discharge across a small gap to heat the air to the point where it glows — the same principle as lightning. Later, the filament light bulb was introduced: this relies on the current causing a thin, coiled wire to glow white-hot. Modern, energy-saving light bulbs pass a high voltage current through a thin gas, causing it to emit ultraviolet light, which strikes a fluorescent coating to produce visible light.

When a conducting material, such as a copper wire, is moved in a magnetic field, a current is generated. Conversely, a current flowing through a wire will, if it experiences a magnetic field, produce movement. This is the principle behind an electric motor. These devices consist of an arrangement of magnets and coils of copper wire such that when a current flows through the wire, a turning motion is produced. Electric motors are widely used in industry and in the home, for example in washing machines and DVD players.

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Measuring Electrical Energy

Energy is measured in joules, a term named after the physicist James Prescott Joule. One joule is roughly the amount of energy required to lift a one pound (0.45 kilogram) weight a vertical distance of nine inches (22.9 cm). It is, however, usually more convenient to think of electricity in terms of power, which is energy divided by time, or the rate at which it flows. This gives the possibly more familiar unit of the watt, named after the scientist James Watt. One watt is equivalent to one joule per second.

There are a number of other units that relate to electricity. The coulomb is the unit of electrical charge. It can be regarded as a quantity of electrons — 1.6 x 1019 — since all electrons have the same, very small, charge. The ampere, usually abbreviated to “amp”, is the unit of electric current, or the number of electrons that flow in a given amount of time. One amp is equivalent to one coulomb per second.

The volt is the unit of electromotive force, or the amount of energy that is transferred per unit of charge, or coulomb. One volt is equivalent to one joule of energy being transferred for each coulomb of charge. Power, in watts, is equivalent to volts multiplied by amps, so a five amp current at 100 volts would be equivalent to 500 watts.

Generating Electrical Energy

Most electricity is generated by devices that convert rotational motion into electrical energy, using the same principle as an electric motor, but in reverse. The movement of coils of wire within a magnetic field produces an electric current. Commonly, heat, often generated by the burning offossil fuels, is used to produce steam that powers a turbine to provide the rotational motion. In a nuclear power plant, nuclear energy provides the heat. Hydroelectric power uses the movement of water under gravity to drive the turbine.

The electricity generated at power plants is generally in the form of alternating current (AC). This means that the current is constantly reversing its direction, many times per second. For most purposes, AC works well, and this is how electricity reaches the home. Some industrial processes, however, require direct current (DC), which flows in one direction only. For example, the manufacture of certain chemicals uses electrolysis: the splitting of compounds into elements or simpler compounds using electricity. This requires direct current, so these industries will either require AC to DC conversion or will have their own DC supply.

It is more efficient to transmit electricity through power lines at higher voltages. For this reason, generating plants use devices called transformers to increase the voltage for transmission. This does not increase the energy or power: when the voltage is raised, the current is reduced and vice versa. Long distance transmission of electricity takes place at many thousands of volts; however, it cannot be used in homes at these voltages. Local transformers reduce the voltage to around 110 volts in the USA, and 220-240 volts in Europe, for domestic supplies.

Electricity for small, low power devices is often supplied by batteries. These use chemical energy to generate a relatively small electric current. They always generate a direct current, and therefore have a negative and a positive terminal. Electrons flow from the negative to the positive terminal when a circuit is completed.


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What Is an Electric Current?

Electric current is measured using an ammeter.
Electric current is measured using an ammeter.

Electric current is the name for the flow of electrons that makes up the movement of electric charge. Current flows when the voltage on one end of a conductor differs from the voltage on the other end of a conductor. A force that most people deal with nearly every day, flowing current includes lighting, electrical power cords, and the surprising shock that comes from shuffling shoes on carpet in dry weather. This force is measured in units called amperes, also called amps.

A ubiquitous presence in modern life, current can be found flowing through conductors. Conductors include metal like aluminum, copper, and steel, but water can also conduct current. Electric current has proved to be quite useful to people, but it can also pose a danger to life and property. As humans are made up largely of water, this means that they can conduct current as well, which puts them at risk for electric injury if they come into contact with a conductor with an electric charge. They can also be injured if they are in contact with a body of water when it has a charge, even if the water is in the form of a small stream or puddle.

When referring to electric current, it is proper to say that the current flows through a conducting object like a wire or appliance, not in it. Insulation like rubber or ceramic is commonly used to keep current from flowing into nearby conductors. While air acts as insulation for wires that do not have contact with conductors, open-air wires must often be insulated at connecting points like transformers or building entry and exit points.


An ampere, or amp, is the standard unit used to measure electric current. On paper, amperes can be calculated from coulombs by dividing the coulombs by one second. Amperes in electric current are measured using a tool called an ammeter. In equations, electric current is often referred to as I, which is used to stand for the intensity of current before the term was shortened to electric current.

Lightning is a form of electric current.
Lightning is a form of electric current.

Electric current can cause fire. When it comes in the form of lightning, this force can set fire to foliage and damage buildings. To prevent lightning damage to buildings in areas prone to lightning storms, building owners often install devices called lightning rods that attract the lightning charge to a high metal rod, which redirects and dispels the current underground. Desert electrical storms that produce lightning with no rain can set fire to dry brush that can grow to damage many homes and acres of land.

Voltage measures the energy that is carried by an electric charge. Voltage is measured in volts. The flow of electricity is often compared to the flow of water, and voltage is the electric equivalent of water pressure. The higher the voltage, the faster electrons will flow through the conductor.

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