Electricity is the result of the interaction of subatomic particles with the electromagnetic force. It is essential to modern industry, technology, and domestic life. Electricity is generated by converting rotational motion into electrical energy, and it is usually transmitted in the form of alternating current. The unit of measurement for electricity includes joules, watts, coulombs, amps, and volts. Electricity can be converted into heat, light, and motion, and it is commonly used in various devices such as motors, televisions, and computers.
Electricity comes from the movement of an electric charge and is commonly called simply “electricity”. Ultimately, it has its origin in the electromagnetic force: one of the four fundamental forces of nature and the one responsible for the behavior of electrically charged objects. Electricity 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. Humans’ ability to generate, transmit and store electricity is crucial to modern industry, technology and, in most countries, domestic life.
The origin of electricity
There are two types of electric charges, called positive and negative. If two electrically charged objects are brought close to each other, 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 each other. If they have different charges, they attract each other. This repulsion or attraction is known as an electromagnetic force and can be harnessed to create a flow of electrical energy.
Atoms consist of a nucleus containing positively charged protons, with negatively charged electrons orbiting it. Protons normally stay in the nucleus, but electrons can move from one atom to another, 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, electrons will flow from a negatively charged area to a positively charged area, if allowed, creating an electric current.
Use of electricity
Electricity is useful both in its own right and as a means of transferring energy over long distances. It is essential for various industrial processes, telecommunications and the Internet, computers, televisions and many other commonly used devices. 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, like 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 stoves, ranges and ovens, for example.
Electricity 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 that causes a thin, coiled wire to emit incandescent light. 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 conductive material, such as copper wire, is moved in a magnetic field, a current is generated. Conversely, a current flowing through a wire, if it experiences a magnetic field, will produce motion. This is the principle behind an electric motor. These devices consist of an arrangement of magnets and copper wire coils such that when a current flows through the wire, a rotational motion is produced. Electric motors are used extensively in industry and in the home, for example in washing machines and DVD players.
Electricity measurement
Energy is measured in joules, a term named after physicist James Prescott Joules. A joule is roughly the amount of energy required to lift a one-pound weight (0.45 kilograms) a vertical distance of nine inches (22.9 cm). However, it’s usually more convenient to think of electricity in terms of power, which is energy divided by time, or by the rate at which it flows. This gives perhaps the most familiar unit of the watt, named after the scientist James Watt. One watt equals one joule per second.
There are a number of other units that refer to electricity. The coulomb is the unit of measure for electric charge. It can be thought of 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 measurement of electric current, ie the number of electrons flowing in a given amount of time. One amp equals one coulomb per second.
The volt is the unit of electromotive force, or the amount of energy that is transferred per unit charge, or coulomb. One volt equals one joule of energy transferred for each coulomb of charge. Power, in watts, is equivalent to volts multiplied by amperes, so a current of five amperes at 100 volts would be equivalent to 500 watts.
Electricity generation
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 in a magnetic field produces an electric current. Commonly, heat, often generated from the burning of fossil fuels, is used to produce steam that powers a turbine to provide rotational motion. In a nuclear power plant, nuclear energy provides the heat. Hydroelectricity uses the movement of water by gravity to drive the turbine.
The electricity generated in power plants is usually in the form of alternating current (AC). This means that the current is constantly reversing its direction, many times per second. For most purposes, the AC works well, and that’s how the electricity reaches the house. Some industrial processes, however, require direct current (DC), which flows in only one direction. For example, the production of some chemicals uses electrolysis – the splitting of compounds into simpler elements or compounds using electricity. This requires DC power, so these industries will either require AC to DC conversion or have their own DC power.
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 transmission voltage. This does not increase energy or power: as voltage goes up, current goes down and vice versa. Long-distance transmission of electricity occurs at many thousands of volts; however, it cannot be used in homes at these voltages. Local transformers step down to around 110 volts in the US 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 terminal to the positive terminal when a circuit is completed.
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