How to Save Electricity by Correct Use of Electrical Appliances

Energy efficient appliances such as refrigerators, dishwashers and freezers will work even more efficiently with some of these energy saving tips.

The world's financial crisis aside, the issue of global warming is one that needs to be taken seriously. Proper use of electrical appliances can be kind to the environment and put some money back into one's pocket.

Energy Saving Tips for Dishwashers

• Energy consumption can be reduced by turning off the dishwasher before the drying cycle. Clean dishes can be left to dry or wiped dry.
• Make sure the dishwasher is not partially loaded, but filled properly.
• Short wash cycles, rinse-only cycles mid-cycle turn off and other features are designed by washing machine manufacturers for energy conservation; make use of them to cut down on electricity.
• Use a cold wash unless it's absolutely necessary to use hot.
• Keep dishwasher filters clear of debris. A blocked filter reduces efficiency and wastes energy.

Energy Saving Tips for Refrigerators

• Choose a refrigerator based on the needs of one's family. Refrigerators work best when filled, so having a giant fridge for two people is obviously not energy-efficient.
• Do not set freezing temperatures lower than necessary – that wastes as much electricity as excessive heat.
• Opening and closing the refrigerator door needlessly lets warm air in and makes the refrigerator work harder. Try to remove several items at once.
• Allow enough space around the refrigerator for air circulation. The air carries heat away from the fridge. If air cannot circulate, the fridge will not work efficiently.
• Switch on the energy saving switch if there is one fitted to the refrigerator.
• Empty out, clean and switch off the refrigerator when away on vacation.
• Make sure the seal around the refrigerator is intact.
• Do not place the refrigerator near the stove or against a wall that faces the sun.
• Thick frost on chilling panels affects the cooling ability. If the refrigerator is not a frost-free model, defrost the refrigerator regularly to save energy.
• Keep condenser coils / panels that are usually found at the back of the fridge clean and dust-free.

Energy Saving Tips for Freezers

• Defrosting of chest freezers should be done once or twice a year, upright models two to three times a year. Do not allow frost to exceed 0.6 to 1.3 cm.
• Freezers and refrigerators operate most efficiently when filled to the capacity recommended by the manufacturer.
• Freezers will have to work harder if more than one tenth of the capacity is used to freeze fresh food at any given time.
• Keep the freezer open for a minimum of time, avoid opening and closing to save energy.
• Keep condenser panels at the back of the freezer clean and dust-free for maximum energy efficiency and conservation.

An effort should be made by every person on the planet to reduce the demand for such fuels as coal, oil, gas and electricity. Not only will one save money but help to reduce emissions of carbon dioxide and other pollutants responsible for contributing to global warming.

DONT'S

Do not connect multiple equipments to a single point outlet to avoid excess loading. Do not temper with lines, energy meters, cutouts, meter seals or metering equipments. It is an offence. Do not use bare wires for extending supply from one point to other or from one premise to other. Do not indulge in theft of electrical energy.  It is cognizable offence and attracts penal charges and/ or imprisonment. Do not plant trees below overhead lines. Do not give application before completing the wring in your premises. Do not delay to pay service connections charges and security deposit once the advice for payment is received. Do not pay any cash to the Assessor when he visits your premises for meter reading. Cash payment for electricity charges should be made only at the authorized collection counter during working hours only. Do not shift the meter or meter board without proper sanction by MPPKVVCL. Do not hand over the application to the assessor and don’t send it by ordinary post. Don’t provide space for fixing the meter underneath the staircase or outside the building.

DO’S

1. In case of any leakage in power supply, get it rectified immediately. Replace defective electrical fittings and appliances promptly.  Avoid loose connections & joints.
2. Install safety equipments for Earth leakage/Over load and Short circuit protection.  Near point of supply.
3. Use proper capacity fuse wire and ensure healthy earthlings at the premises.
4. Get the wiring done through licensed Electrical contractors.
5. Use ISI marked equipments and cables of proper capacity even they cost more.
6. Ensure safety of meter and metering equipments. Prefer waterproof enclosures for them.
7. Construct building with proper clearance from HT/LT tension lines as per IER 1956.
8. Use electricity only for purpose for which the service connection has been given.
9. If energy meter is found stopped/defective please bring the matter in knowledge of MPPKVVCL authorities immediately in writing.
10. Pay energy bills regularly at authorized cash counters only within due date to avoid inconvenience due to disconnection.
11. For any difficulties related to electricity supply, always contract MPPKVVCL authorities at their offices.
12. Observe safety precautions to avoid electrical accidents.
13. Stay away from a downed power line and informed MPPKVVCL office immediately.
14. Beware of sub-station & transmission lines stay clear of sub-station, poles, towers structures.

Tips for electricity consumers

1. Make use of daylight and natural ventilation to maximum and avoid to use bulbs or tube lights during daytime.
2. Switch off light and fans if not in use. Reduce high wattage bulbs where less light is needed.
3. Avoid unnecessary decoration of lights.
4. In a vacant house, limit the use of electricity as per minimum requirement.
5. Switch on or off the streetlights in proper time.
6. Buy the electrical equipments, which use less electricity and are energy efficient
7. In air conditioned buildings and houses, keep the doors and windows close to save electricity. Clean A.C. filter regularly.
8. Use electronic regulators in fans, use 36-watt thin tube light instead of 40-watt tube light.
9. Use fluorescent lights in place of bulb to reduce consumption of electricity.
10. Use standard pins to tap supply from plug points. Avoid tapping supply by inserting bare  wires.
11. Do not use lamp fittings to tie wires or ropes to dry cloths.
12. Replace fuse bulb after switch is off.
13. Defrost the fridge once ice gets more then ¼” thick. Regular defrosting reduces power consumption. Place the fridge with its coils at distance from wall so that the coils can have sufficient space to breathe. Do place the refrigerator near any heat source.
14. Use of light colour on walls reduces lighting requirement
15. Make home safe for children against electrical hazards. Install plastic protective caps on plug points.
16. Electricity and water can be a deadly combination Always remember that water and electricity must never mix.
17. Use foot valves of less resistance in tube well to reduce the consumption of electricity.
18. To avoid damage of bearings try to keep motor and pump in a straight line. This will reduce wastage of energy.
19. Use good quality PVC suction pipe to save energy.
20. Use appropriate pump sets, keeping in mind the height and capacity of pipe.
21. To improve the power factor and voltage use shunt capacitor with motor. This will also save the electricity.
22. Energy is lost by belts.  Minimize the use of belts.
23. Keep the motor near load.
24. To improve power factor and so the voltage, use shunt capacitors with motor. This will also reduce the consumption of electricity.
25. The damaged bearings waste energy, change them immediately.
26. Use motors with good capacity and size.
27. Use one motor of appropriate capacity for one work.
28. Avoid loading of vehicles like trucks beyond the permissible height.  This may cause electrical accident due to coming of vehicle in contact with electrical lines.
29. Don’t mount/tie advertisement boards, flags etc on electric poles.
30. Place “Men working’ sign boards on all switches before start working.
31. Place rubber mats in front of electrical switchboard.
32. Keep the fire extinguisher is good condition. Check them periodically.

65 WAYS TO SAVE ELECTRICITY

KEEP YOUR ELECTRICITY BILLS DOWN AND SAVE ENERGY FOR THE FUTURE BY BEING AWARE OF THE MOST EFFICIENT WAYS TO USE ELECTRICITY.

COOKING

1 Keep the door closed. Ever time you open it the temperature drop about 20 degrees (c)
2 Cook several dishes at the one time.If you are cooking small items use the frypan.
3 When cooking small quantities use one sauce pan with dividers.
4 Keep food warm at 70-80 deg(c) Higher temperatures waste electricity and over cook food.
5 Use oven heat for plate warming.
6 Use utensils with flat bottoms and well fitting lids.Make sure they cover hotplates.
7 To cook vegetables the water doesn't need to be boiling furiously - a gentle simmer is enough.


8 Fan type ovens reduce cooking costs.
9 Use bright clean hotplate reflectors to send the heat upwards where it is wanted.
10 Pressure cookers can save up to 25% of power.
11 Use small appliances eg. griller,crockpot,wok,etc for appropriate foods.
12 Thaw frozen foods before cooking - this saves about 15 minutes cooking per 450 grams (one pound).
13 A microwave is very economical for suitable functions -it is excellent for reconstituting food.
14 Don't use grill-boiler plate on top of range for utensils not large enough to cover it.
15 Don't boil water on a hotplate - use an electric kettle.
16 Make sure your oven door seals properly.

HEATING AND COOLING.

17 Have the ceiling insulated with at least 50mm of fibrous or foam insulation.
18 In timber framed or brick homes the walls should also be insulated. Block off any chimneys not being used - A lot of heat is lost there.
19 Unless you have full home conditioning close the doors of the room/s being heated or cooled. Doors and windows should fit well because draughts can waste a lot of energy. Close curtains to stop heat escaping.
20 See that air- conditioner filters and condenser coils are kept clean.
21 Reverse cycle air-conditioners provide 2 to 2.5 times as much heat as an element type heater for the same electricity consumption.


22 Zoning of a house conditioned by a ducted system can cut energy consumption to a half or even third.
23 Shade windows during summer to keep sun of the glass.
24 Don't leave heating or cooling appliances on when rooms are unoccupied.
25 Use personal fans and ceiling fans for relief from hot weather. Fans cost much less to run than air conditioners.
26 Many air- conditioning systems operate at 22 deg (c). You will still be comfortable if you set the control for 24-25 deg (c) in summer. and 18-19 deg (c) in winter and you will use a lot less electricity.


27 Leave room conditioner "fresh air " and "exhaust air " controls in the closed positions unless you want to freshen thew room air.
28 Set fan at high speed for a room conditioner to work most efficiently.
29 Evaporative coolers are very effective when installed correctly. The operating cost of an evaporative cooler is only a fraction of that of a refrigerated unit.
30 A student can be kept warm with a 150 watt infra red lamp fitted under the desk.
31 Localised under carpet heating gives economical armchair comfort.
32 People heating is more economical than space heating.-use radiators multi-heat radiant heaters, wall strip heaters ,fan heaters.
33 Electric blankets are the cheapest form of bedroom heating.

REFRIGERATION

34 Select a fridge that uses waste heat for defrosting etc. These fridges are usually cheaper to operate.
35 Buy the size you need extra capacity uses extra power.
36 If you already have a chest or upright freezer buy an "all though " refrigerator instead of a fridge freezer combination.

37 Defrost before the ice build up is 1 cm thick.
38 Open the door only when necessary.
39 Make sure the door seals well. If a piece of paper will slide easily between the cabinet and the door seal is not good enough.

40 Keep dust and fluff brushed off the coils on the back or bottom of the fridge.
41 Put the fridge in a well ventilated position.
42 Place your fridge away from direct sunlight or any source of heat. Don't put hot food into a fridge or freezer.

CLOTHES AND WASHING

43 Don't buy a large machine if you don't need it. For the occasional big wash an extra cycle or two is cheaper than under using a large washer.
44 Adjust the water level to economically wash a partial load.Otherwise it is better to wait until you have a full load.But don't overload your machine.

45 Your washer may have features than can save your money.Soak cycles remove stubborn stains in wash cycle.Suds savers allow you to re use hot water.
46 Use correct type of detergent and cold or tepid water will wash clothes effectively.

LIGHTING

47 Good lighting means avoiding glare and gloom by using the right amount of light in the right way.

48 Use light translucent shades- opaque or dark shades require bigger lamps.
49 Use a good local light near the task. It is more effective and more efficient than a large central light.
50 Use fluorescent tubes . they use about a quarter of electricity used by ordinary globes and they last
about eight times as long. They CAN be switched on and off as often as you need without affecting operating cost.

CLOTHES DRYING

51 Use solar energy to dry your clothes -it costs nothing.
52 Operate your dryer using the fan alone. Only switch the heater on if it is really necessary.Vent the dryer outside the house and don't let lint block the vent.

53 never overload or underload the dryer - you get most economical operation with the correct load.
54 Switch off when the clothes are dry enough - over drying makes them feel harsh and waste electricity.
55 Tumble dryers are more effective than cabinet dryers.

WATER HEATING

56 Off peak low pressure storage heaters are generally the cheapest overall.

57 Don't allow dripping taps .Sixty drips a minutes means about 1200 litres a month drown the drain.
And you have paid for it to be heated.
58 Water restrictors and low flow shower nozzles will help to save water.
59 Insulate hot water pipes from storage heaters for at least a metre from the heater as heat can be conducted along these pipes and lost to the atmosphere.

60 Install a storage heater of 125 litres or more to run off peak tariff - which is about half the normal rate.
61 Normally you will use less water for shower than bath.
62 Fill your electric kettle or jug from the cold tap.Running off a lot of cold water from the hot pipes is wasteful and expensive.
63 Don't have you hot water set too 70 deg (c) is usually hot enough . Otherwise it costs more to heat the water and it loses more heat while being stored.

ACCESSORIES

64 Dimmers save power and enable you to obtain pleasant changes of mood in your lighting.
65 Use plug-in timers to control such things as fryingpans,crockpots,riadiators.lights and air conditioners.

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Cultural perception

In the 19th and early 20th century, electricity was not part of the everyday life of many people, even in the industrialised Western world. The popular culture of the time accordingly often depicts it as a mysterious, quasi-magical force that can slay the living, revive the dead or otherwise bend the laws of nature.^[76] This attitude began with the 1771 experiments of Luigi Galvani in which the legs of dead frogs were shown to twitch on application of animal electricity. "Revitalization" or resuscitation of apparently dead or drowned persons was reported in the medical literature shortly after Galvani's work. These results were known to Mary Shelley when she authored Frankenstein (1819), although she does not name the method of revitalization of the monster. The revitalization of monsters with electricity later became a stock theme in horror films.
As the public familiarity with electricity as the lifeblood of the Second Industrial Revolution grew, its wielders were more often cast in a positive light,^[77] such as the workers who "finger death at their gloves' end as they piece and repiece the living wires" in Rudyard Kipling's 1907 poem Sons of Martha.^[77] Electrically powered vehicles of every sort featured large in adventure stories such as those of Jules Verne and the Tom Swift books.^[77] The masters of electricity, whether fictional or real—including scientists such as Thomas Edison, Charles Steinmetz or Nikola Tesla—were popularly conceived of as having wizard-like powers.^[77]
With electricity ceasing to be a novelty and becoming a necessity of everyday life in the later half of the 20th century, it required particular attention by popular culture only when it stops flowing,^[77] an event that usually signals disaster.^[77] The people who keep it flowing, such as the nameless hero of Jimmy Webb’s song "Wichita Lineman" (1968),^[77] are still often cast as heroic, wizard-like figures.^[77]

Electrical phenomena in nature

Electricity is not a human invention, and may be observed in several forms in nature, a prominent manifestation of which is lightning. Many interactions familiar at the macroscopic level, such as touch, friction or chemical bonding, are due to interactions between electric fields on the atomic scale. The Earth's magnetic field is thought to arise from a natural dynamo of circulating currents in the planet's core.^[71] Certain crystals, such as quartz, or even sugar, generate a potential difference across their faces when subjected to external pressure.^[72] This phenomenon is known as piezoelectricity, from the Greek piezein (πιέζειν), meaning to press, and was discovered in 1880 by Pierre and Jacques Curie. The effect is reciprocal, and when a piezoelectric material is subjected to an electric field, a small change in physical dimensions take place.^[72]
Some organisms, such as sharks, are able to detect and respond to changes in electric fields, an ability known as electroreception,^[73] while others, termed electrogenic, are able to generate voltages themselves to serve as a predatory or defensive weapon.^[3] The order Gymnotiformes, of which the best known example is the electric eel, detect or stun their prey via high voltages generated from modified muscle cells called electrocytes.^[3][4] All animals transmit information along their cell membranes with voltage pulses called action potentials, whose functions include communication by the nervous system between neurons and muscles.^[74] An electric shock stimulates this system, and causes muscles to contract.^[75] Action potentials are also responsible for coordinating activities in certain plants and mammals.^[74]

Production and uses

Thales' experiments with amber rods were the first studies into the production of electrical energy. While this method, now known as the triboelectric effect, is capable of lifting light objects and even generating sparks, it is extremely inefficient.^[50] It was not until the invention of the voltaic pile in the eighteenth century that a viable source of electricity became available. The voltaic pile, and its modern descendant, the electrical battery, store energy chemically and make it available on demand in the form of electrical energy.^[50] The battery is a versatile and very common power source which is ideally suited to many applications, but its energy storage is finite, and once discharged it must be disposed of or recharged. For large electrical demands electrical energy must be generated and transmitted continuously over conductive transmission lines.
Electrical power is usually generated by electro-mechanical generators driven by steam produced from fossil fuel combustion, or the heat released from nuclear reactions; or from other sources such as kinetic energy extracted from wind or flowing water. The modern steam turbine invented by Sir Charles Parsons in 1884 today generates about 80 percent of the electric power in the world using a variety of heat sources. Such generators bear no resemblance to Faraday's homopolar disc generator of 1831, but they still rely on his electromagnetic principle that a conductor linking a changing magnetic field induces a potential difference across its ends.^[51] The invention in the late nineteenth century of the transformer meant that electrical power could be transmitted more efficiently at a higher voltage but lower current. Efficient electrical transmission meant in turn that electricity could be generated at centralised power stations, where it benefited from economies of scale, and then be despatched relatively long distances to where it was needed.^[52][53]
Since electrical energy cannot easily be stored in quantities large enough to meet demands on a national scale, at all times exactly as much must be produced as is required.^[52] This requires electricity utilities to make careful predictions of their electrical loads, and maintain constant co-ordination with their power stations. A certain amount of generation must always be held in reserve to cushion an electrical grid against inevitable disturbances and losses.
Demand for electricity grows with great rapidity as a nation modernises and its economy develops. The United States showed a 12% increase in demand during each year of the first three decades of the twentieth century,^[54] a rate of growth that is now being experienced by emerging economies such as those of India or China.^[55][56] Historically, the growth rate for electricity demand has outstripped that for other forms of energy.^[57]
Environmental concerns with electricity generation have led to an increased focus on generation from renewable sources, in particular from wind and hydropower. While debate can be expected to continue over the environmental impact of different means of electricity production, its final form is relatively clean.^[58]

Uses

The light bulb, an early application of electricity, operates by Joule heating: the passage of current through resistance generating heat

Electricity is an extremely flexible form of energy, and has been adapted to a huge, and growing, number of uses.^[59] The invention of a practical incandescent light bulb in the 1870s led to lighting becoming one of the first publicly available applications of electrical power. Although electrification brought with it its own dangers, replacing the naked flames of gas lighting greatly reduced fire hazards within homes and factories.^[60] Public utilities were set up in many cities targeting the burgeoning market for electrical lighting.
The Joule heating effect employed in the light bulb also sees more direct use in electric heating. While this is versatile and controllable, it can be seen as wasteful, since most electrical generation has already required the production of heat at a power station.^[61] A number of countries, such as Denmark, have issued legislation restricting or banning the use of electric heating in new buildings.^[62] Electricity is however a highly practical energy source for refrigeration,^[63] with air conditioning representing a growing sector for electricity demand, the effects of which electricity utilities are increasingly obliged to accommodate.^[64]
Electricity is used within telecommunications, and indeed the electrical telegraph, demonstrated commercially in 1837 by Cooke and Wheatstone, was one of its earliest applications. With the construction of first intercontinental, and then transatlantic, telegraph systems in the 1860s, electricity had enabled communications in minutes across the globe. Optical fibre and satellite communication technology have taken a share of the market for communications systems, but electricity can be expected to remain an essential part of the process.
The effects of electromagnetism are most visibly employed in the electric motor, which provides a clean and efficient means of motive power. A stationary motor such as a winch is easily provided with a supply of power, but a motor that moves with its application, such as an electric vehicle, is obliged to either carry along a power source such as a battery, or to collect current from a sliding contact such as a pantograph, placing restrictions on its range or performance.
Electronic devices make use of the transistor, perhaps one of the most important inventions of the twentieth century,^[65] and a fundamental building block of all modern circuitry. A modern integrated circuit may contain several billion miniaturised transistors in a region only a few centimetres square.^[66]

Electricity is also used to fuel public transportation, including electric busses and trains. ^[67]

Electric circuits

An electric circuit is an interconnection of electric components such that electric charge is made to flow along a closed path (a circuit), usually to perform some useful task.
The components in an electric circuit can take many forms, which can include elements such as resistors, capacitors, switches, transformers and electronics. Electronic circuits contain active components, usually semiconductors, and typically exhibit non-linear behaviour, requiring complex analysis. The simplest electric components are those that are termed passive and linear: while they may temporarily store energy, they contain no sources of it, and exhibit linear responses to stimuli.^[49]
The resistor is perhaps the simplest of passive circuit elements: as its name suggests, it resists the current through it, dissipating its energy as heat. The resistance is a consequence of the motion of charge through a conductor: in metals, for example, resistance is primarily due to collisions between electrons and ions. Ohm's law is a basic law of circuit theory, stating that the current passing through a resistance is directly proportional to the potential difference across it. The resistance of most materials is relatively constant over a range of temperatures and currents; materials under these conditions are known as 'ohmic'. The ohm, the unit of resistance, was named in honour of Georg Ohm, and is symbolised by the Greek letter Ω. 1 Ω is the resistance that will produce a potential difference of one volt in response to a current of one amp.^[49]
The capacitor is a device capable of storing charge, and thereby storing electrical energy in the resulting field. Conceptually, it consists of two conducting plates separated by a thin insulating layer; in practice, thin metal foils are coiled together, increasing the surface area per unit volume and therefore the capacitance. The unit of capacitance is the farad, named after Michael Faraday, and given the symbol F: one farad is the capacitance that develops a potential difference of one volt when it stores a charge of one coulomb. A capacitor connected to a voltage supply initially causes a current as it accumulates charge; this current will however decay in time as the capacitor fills, eventually falling to zero. A capacitor will therefore not permit a steady state current, but instead blocks it.^[49]
The inductor is a conductor, usually a coil of wire, that stores energy in a magnetic field in response to the current through it. When the current changes, the magnetic field does too, inducing a voltage between the ends of the conductor. The induced voltage is proportional to the time rate of change of the current. The constant of proportionality is termed the inductance. The unit of inductance is the henry, named after Joseph Henry, a contemporary of Faraday. One henry is the inductance that will induce a potential difference of one volt if the current through it changes at a rate of one ampere per second.^[49] The inductor's behaviour is in some regards converse to that of the capacitor: it will freely allow an unchanging current, but opposes a rapidly changing one.

Electromagnetism

Ørsted's discovery in 1821 that a magnetic field existed around all sides of a wire carrying an electric current indicated that there was a direct relationship between electricity and magnetism. Moreover, the interaction seemed different from gravitational and electrostatic forces, the two forces of nature then known. The force on the compass needle did not direct it to or away from the current-carrying wire, but acted at right angles to it.^[30] Ørsted's slightly obscure words were that "the electric conflict acts in a revolving manner." The force also depended on the direction of the current, for if the flow was reversed, then the force did too.^[45]
Ørsted did not fully understand his discovery, but he observed the effect was reciprocal: a current exerts a force on a magnet, and a magnetic field exerts a force on a current. The phenomenon was further investigated by Ampère, who discovered that two parallel current-carrying wires exerted a force upon each other: two wires conducting currents in the same direction are attracted to each other, while wires containing currents in opposite directions are forced apart.^[46] The interaction is mediated by the magnetic field each current produces and forms the basis for the international definition of the ampere.^[46]

The electric motor exploits an important effect of electromagnetism: a current through a magnetic field experiences a force at right angles to both the field and current

This relationship between magnetic fields and currents is extremely important, for it led to Michael Faraday's invention of the electric motor in 1821. Faraday's homopolar motor consisted of a permanent magnet sitting in a pool of mercury. A current was allowed through a wire suspended from a pivot above the magnet and dipped into the mercury. The magnet exerted a tangential force on the wire, making it circle around the magnet for as long as the current was maintained.^[47]
Experimentation by Faraday in 1831 revealed that a wire moving perpendicular to a magnetic field developed a potential difference between its ends. Further analysis of this process, known as electromagnetic induction, enabled him to state the principle, now known as Faraday's law of induction, that the potential difference induced in a closed circuit is proportional to the rate of change of magnetic flux through the loop. Exploitation of this discovery enabled him to invent the first electrical generator in 1831, in which he converted the mechanical energy of a rotating copper disc to electrical energy.^[47] Faraday's disc was inefficient and of no use as a practical generator, but it showed the possibility of generating electric power using magnetism, a possibility that would be taken up by those that followed on from his work.
Faraday's and Ampère's work showed that a time-varying magnetic field acted as a source of an electric field, and a time-varying electric field was a source of a magnetic field. Thus, when either field is changing in time, then a field of the other is necessarily induced.^[48] Such a phenomenon has the properties of a wave, and is naturally referred to as an electromagnetic wave. Electromagnetic waves were analysed theoretically by James Clerk Maxwell in 1864. Maxwell developed a set of equations that could unambiguously describe the interrelationship between electric field, magnetic field, electric charge, and electric current. He could moreover prove that such a wave would necessarily travel at the speed of light, and thus light itself was a form of electromagnetic radiation. Maxwell's Laws, which unify light, fields, and charge are one of the great milestones of theoretical physics.^[48]

Electric potential

The concept of electric potential is closely linked to that of the electric field. A small charge placed within an electric field experiences a force, and to have brought that charge to that point against the force requires work. The electric potential at any point is defined as the energy required to bring a unit test charge from an infinite distance slowly to that point. It is usually measured in volts, and one volt is the potential for which one joule of work must be expended to bring a charge of one coulomb from infinity.^[42] This definition of potential, while formal, has little practical application, and a more useful concept is that of electric potential difference, and is the energy required to move a unit charge between two specified points. An electric field has the special property that it is conservative, which means that the path taken by the test charge is irrelevant: all paths between two specified points expend the same energy, and thus a unique value for potential difference may be stated.^[42] The volt is so strongly identified as the unit of choice for measurement and description of electric potential difference that the term voltage sees greater everyday usage.
For practical purposes, it is useful to define a common reference point to which potentials may be expressed and compared. While this could be at infinity, a much more useful reference is the Earth itself, which is assumed to be at the same potential everywhere. This reference point naturally takes the name earth or ground. Earth is assumed to be an infinite source of equal amounts of positive and negative charge, and is therefore electrically uncharged—and unchargeable.^[43]
Electric potential is a scalar quantity, that is, it has only magnitude and not direction. It may be viewed as analogous to height: just as a released object will fall through a difference in heights caused by a gravitational field, so a charge will 'fall' across the voltage caused by an electric field.^[44] As relief maps show contour lines marking points of equal height, a set of lines marking points of equal potential (known as equipotentials) may be drawn around an electrostatically charged object. The equipotentials cross all lines of force at right angles. They must also lie parallel to a conductor's surface, otherwise this would produce a force that will move the charge carriers to even the potential of the surface.
The electric field was formally defined as the force exerted per unit charge, but the concept of potential allows for a more useful and equivalent definition: the electric field is the local gradient of the electric potential. Usually expressed in volts per metre, the vector direction of the field is the line of greatest slope of potential, and where the equipotentials lie closest together.^[17]

Electric field

The concept of the electric field was introduced by Michael Faraday. An electric field is created by a charged body in the space that surrounds it, and results in a force exerted on any other charges placed within the field. The electric field acts between two charges in a similar manner to the way that the gravitational field acts between two masses, and like it, extends towards infinity and shows an inverse square relationship with distance.^[22] However, there is an important difference. Gravity always acts in attraction, drawing two masses together, while the electric field can result in either attraction or repulsion. Since large bodies such as planets generally carry no net charge, the electric field at a distance is usually zero. Thus gravity is the dominant force at distance in the universe, despite being much weaker.^[23]

Field lines emanating from a positive charge above a plane conductor

An electric field generally varies in space,^[34] and its strength at any one point is defined as the force (per unit charge) that would be felt by a stationary, negligible charge if placed at that point.^[35] The conceptual charge, termed a 'test charge', must be vanishingly small to prevent its own electric field disturbing the main field and must also be stationary to prevent the effect of magnetic fields. As the electric field is defined in terms of force, and force is a vector, so it follows that an electric field is also a vector, having both magnitude and direction. Specifically, it is a vector field.^[35]
The study of electric fields created by stationary charges is called electrostatics. The field may be visualised by a set of imaginary lines whose direction at any point is the same as that of the field. This concept was introduced by Faraday,^[36] whose term 'lines of force' still sometimes sees use. The field lines are the paths that a point positive charge would seek to make as it was forced to move within the field; they are however an imaginary concept with no physical existence, and the field permeates all the intervening space between the lines.^[36] Field lines emanating from stationary charges have several key properties: first, that they originate at positive charges and terminate at negative charges; second, that they must enter any good conductor at right angles, and third, that they may never cross nor close in on themselves.^[37]
A hollow conducting body carries all its charge on its outer surface. The field is therefore zero at all places inside the body.^[38] This is the operating principal of the Faraday cage, a conducting metal shell which isolates its interior from outside electrical effects.
The principles of electrostatics are important when designing items of high-voltage equipment. There is a finite limit to the electric field strength that may be withstood by any medium. Beyond this point, electrical breakdown occurs and an electric arc causes flashover between the charged parts. Air, for example, tends to arc across small gaps at electric field strengths which exceed 30 kV per centimetre. Over larger gaps, its breakdown strength is weaker, perhaps 1 kV per centimetre.^[39] The most visible natural occurrence of this is lightning, caused when charge becomes separated in the clouds by rising columns of air, and raises the electric field in the air to greater than it can withstand. The voltage of a large lightning cloud may be as high as 100 MV and have discharge energies as great as 250 kWh.^[40]
The field strength is greatly affected by nearby conducting objects, and it is particularly intense when it is forced to curve around sharply pointed objects. This principle is exploited in the lightning conductor, the sharp spike of which acts to encourage the lightning stroke to develop there, rather than to the building it serves to protect.^[41]

Electric current

The movement of electric charge is known as an electric current, the intensity of which is usually measured in amperes. Current can consist of any moving charged particles; most commonly these are electrons, but any charge in motion constitutes a current.
By historical convention, a positive current is defined as having the same direction of flow as any positive charge it contains, or to flow from the most positive part of a circuit to the most negative part. Current defined in this manner is called conventional current. The motion of negatively charged electrons around an electric circuit, one of the most familiar forms of current, is thus deemed positive in the opposite direction to that of the electrons.^[27] However, depending on the conditions, an electric current can consist of a flow of charged particles in either direction, or even in both directions at once. The positive-to-negative convention is widely used to simplify this situation.

An electric arc provides an energetic demonstration of electric current

The process by which electric current passes through a material is termed electrical conduction, and its nature varies with that of the charged particles and the material through which they are travelling. Examples of electric currents include metallic conduction, where electrons flow through a conductor such as metal, and electrolysis, where ions (charged atoms) flow through liquids. While the particles themselves can move quite slowly, sometimes with an average drift velocity only fractions of a millimetre per second,^[17] the electric field that drives them itself propagates at close to the speed of light, enabling electrical signals to pass rapidly along wires.^[28]
Current causes several observable effects, which historically were the means of recognising its presence. That water could be decomposed by the current from a voltaic pile was discovered by Nicholson and Carlisle in 1800, a process now known as electrolysis. Their work was greatly expanded upon by Michael Faraday in 1833.^[29] Current through a resistance causes localised heating, an effect James Prescott Joule studied mathematically in 1840.^[29] One of the most important discoveries relating to current was made accidentally by Hans Christian Ørsted in 1820, when, while preparing a lecture, he witnessed the current in a wire disturbing the needle of a magnetic compass.^[30] He had discovered electromagnetism, a fundamental interaction between electricity and magnetics.
In engineering or household applications, current is often described as being either direct current (DC) or alternating current (AC). These terms refer to how the current varies in time. Direct current, as produced by example from a battery and required by most electronic devices, is a unidirectional flow from the positive part of a circuit to the negative.^[31] If, as is most common, this flow is carried by electrons, they will be travelling in the opposite direction. Alternating current is any current that reverses direction repeatedly; almost always this takes the form of a sinusoidal wave.^[32] Alternating current thus pulses back and forth within a conductor without the charge moving any net distance over time. The time-averaged value of an alternating current is zero, but it delivers energy in first one direction, and then the reverse. Alternating current is affected by electrical properties that are not observed under steady state direct current, such as inductance and capacitance.^[33] These properties however can become important when circuitry is subjected to transients, such as when first energised.

Electric charge

Electric charge is a property of certain subatomic particles, which gives rise to and interacts with the electromagnetic force, one of the four fundamental forces of nature. Charge originates in the atom, in which its most familiar carriers are the electron and proton. It is a conserved quantity, that is, the net charge within an isolated system will always remain constant regardless of any changes taking place within that system.^[16] Within the system, charge may be transferred between bodies, either by direct contact, or by passing along a conducting material, such as a wire.^[17] The informal term static electricity refers to the net presence (or 'imbalance') of charge on a body, usually caused when dissimilar materials are rubbed together, transferring charge from one to the other.

Charge on a gold-leaf electroscope causes the leaves to visibly repel each other

The presence of charge gives rise to the electromagnetic force: charges exert a force on each other, an effect that was known, though not understood, in antiquity.^[18] A lightweight ball suspended from a string can be charged by touching it with a glass rod that has itself been charged by rubbing with a cloth. If a similar ball is charged by the same glass rod, it is found to repel the first: the charge acts to force the two balls apart. Two balls that are charged with a rubbed amber rod also repel each other. However, if one ball is charged by the glass rod, and the other by an amber rod, the two balls are found to attract each other. These phenomena were investigated in the late eighteenth century by Charles-Augustin de Coulomb, who deduced that charge manifests itself in two opposing forms. This discovery led to the well-known axiom: like-charged objects repel and opposite-charged objects attract.^[18]
The force acts on the charged particles themselves, hence charge has a tendency to spread itself as evenly as possible over a conducting surface. The magnitude of the electromagnetic force, whether attractive or repulsive, is given by Coulomb's law, which relates the force to the product of the charges and has an inverse-square relation to the distance between them.^[19][20] The electromagnetic force is very strong, second only in strength to the strong interaction,^[21] but unlike that force it operates over all distances.^[22] In comparison with the much weaker gravitational force, the electromagnetic force pushing two electrons apart is 10⁴² times that of the gravitational attraction pulling them together.^[23]
The charge on electrons and protons is opposite in sign, hence an amount of charge may be expressed as being either negative or positive. By convention, the charge carried by electrons is deemed negative, and that by protons positive, a custom that originated with the work of Benjamin Franklin.^[24] The amount of charge is usually given the symbol Q and expressed in coulombs;^[25] each electron carries the same charge of approximately −1.6022×10⁻¹⁹ coulomb. The proton has a charge that is equal and opposite, and thus +1.6022×10⁻¹⁹  coulomb. Charge is possessed not just by matter, but also by antimatter, each antiparticle bearing an equal and opposite charge to its corresponding particle.^[26]
Charge can be measured by a number of means, an early instrument being the gold-leaf electroscope, which although still in use for classroom demonstrations, has been superseded by the electronic electrometer.^[17]

History

Long before any knowledge of electricity existed people were aware of shocks from electric fish. Ancient Egyptian texts dating from 2750 BC referred to these fish as the "Thunderer of the Nile", and described them as the "protectors" of all other fish. Electric fish were again reported millennia later by ancient Greek, Roman and Arabic naturalists and physicians.^[2] Several ancient writers, such as Pliny the Elder and Scribonius Largus, attested to the numbing effect of electric shocks delivered by catfish and torpedo rays, and knew that such shocks could travel along conducting objects.^[3] Patients suffering from ailments such as gout or headache were directed to touch electric fish in the hope that the powerful jolt might cure them.^[4] Possibly the earliest and nearest approach to the discovery of the identity of lightning, and electricity from any other source, is to be attributed to the Arabs, who before the 15th century had the Arabic word for lightning (raad) applied to the electric ray.^[5]
Ancient cultures around the Mediterranean knew that certain objects, such as rods of amber, could be rubbed with cat's fur to attract light objects like feathers. Thales of Miletos made a series of observations on static electricity around 600 BC, from which he believed that friction rendered amber magnetic, in contrast to minerals such as magnetite, which needed no rubbing.^[6][7] Thales was incorrect in believing the attraction was due to a magnetic effect, but later science would prove a link between magnetism and electricity. According to a controversial theory, the Parthians may have had knowledge of electroplating, based on the 1936 discovery of the Baghdad Battery, which resembles a galvanic cell, though it is uncertain whether the artifact was electrical in nature.^[8]

Benjamin Franklin conducted extensive research on electricity in the 18th century

Electricity would remain little more than an intellectual curiosity for millennia until 1600, when the English scientist William Gilbert made a careful study of electricity and magnetism, distinguishing the lodestone effect from static electricity produced by rubbing amber.^[6] He coined the New Latin word electricus ("of amber" or "like amber", from ήλεκτρον [elektron], the Greek word for "amber") to refer to the property of attracting small objects after being rubbed.^[9] This association gave rise to the English words "electric" and "electricity", which made their first appearance in print in Thomas Browne's Pseudodoxia Epidemica of 1646.^[10]
Further work was conducted by Otto von Guericke, Robert Boyle, Stephen Gray and C. F. du Fay. In the 18th century, Benjamin Franklin conducted extensive research in electricity, selling his possessions to fund his work. In June 1752 he is reputed to have attached a metal key to the bottom of a dampened kite string and flown the kite in a storm-threatened sky.^[11] A succession of sparks jumping from the key to the back of the hand showed that lightning was indeed electrical in nature.^[12]

Michael Faraday formed the foundation of electric motor technology

In 1791, Luigi Galvani published his discovery of bioelectricity, demonstrating that electricity was the medium by which nerve cells passed signals to the muscles.^[13] Alessandro Volta's battery, or voltaic pile, of 1800, made from alternating layers of zinc and copper, provided scientists with a more reliable source of electrical energy than the electrostatic machines previously used.^[13] The recognition of electromagnetism, the unity of electric and magnetic phenomena, is due to Hans Christian Ørsted and André-Marie Ampère in 1819-1820; Michael Faraday invented the electric motor in 1821, and Georg Ohm mathematically analysed the electrical circuit in 1827.^[13] Electricity and magnetism (and light) were definitively linked by James Clerk Maxwell, in particular in his "On Physical Lines of Force" in 1861 and 1862.^[14]
While it had been the early 19th century that had seen rapid progress in electrical science, the late 19th century would see the greatest progress in electrical engineering. Through such people as Nikola Tesla, Thomas Edison, Ottó Bláthy, Ányos Jedlik, Sir Charles Parsons, Joseph Swan, George Westinghouse, Ernst Werner von Siemens, Alexander Graham Bell and Lord Kelvin, electricity was turned from a scientific curiosity into an essential tool for modern life, becoming a driving force for the Second Industrial Revolution.^[15]