Generation and transmission of electric energy
The potential benefits of electrical energy supplied to a number of consumers from a common generating system were recognized shortly after the development of the ‘dynamo’, commonly known as the generator. The first public power station was put into service in 1882 in London (Holborn). Soon a number of other public supplies for electricity followed in other developed countries. The early systems produced direct ccurrent at low-voltage, but their service was limited to highly localized areas and were used mainly for electric lighting. The limitations of d.c. transmission at low-voltage became readily apparent. By 1890 the art in the development of an a.c. generator and ...
Electrical energy is a form of energyresulting from the flow of electric charge. Energy is the ability to do work or apply force to move an object. In the case of electrical energy, the force is electrical attraction or repulsion between charged particles. Electrical energy may be either potential energy or kinetic energy, but it's usually encountered as potential energy, which is energy stored due to the relative positions of charged particles or electric fields. The movement of charged particles through a wire or other medium is called current or electricity. There is also static electricity, which results from an imbalance or separation of the positive and negative charges on an object. Static electricity is a form of electrical potential energy. If sufficient charge builds up, the electrical energy may be discharged to form a spark (or even lightning), which has electrical kinetic energy. By convention, the direction of an electric field is always shown pointing in the direction a positive particle would move if it was placed in the field. This is important to remember when working with electrical energy, because the most common current carrier is an electron, which moves in the opposite direction compared with a proton.
The British scientist Michael Faraday discovered a mean of generating electricity as early as the 1820s. He moved a loop or disc of conductive metal between the poles of a magnet. The basic principle is that electrons in copper wire are free to move. Each electron carries a negative electrical charge. Its movement is governed by attractive forces between the electron and positive charges (such as protons and positively-charged ions) and repulsive forces between the electron and like-charges (such as other electrons and negatively-charged ions). In other words, the electric field surrounding a charged particle (an electron, in this case) exerts a force on other charged particles, causing it to move and thus do work. Force must be applied to move two attracted charged particles away from each other. Any charged particles may be involved in producing electrical energy, including electrons, protons, atomic nuclei, cations (positively-charged ions), and anions (negatively-charged ions), positrons (antimatter equivalent to electrons), and so on.
Electrical energy used for electric power, such as wall current used to light a light bulb or power a computer, is energy that is converted from electric potential energy. This potential energy is converted into another type of energy (heat, light, mechanical energy, etc.). For a power utility, the motion of electrons in wire produces the current and electric potential. A battery is another source of electrical energy, except the electrical charges may be ions in a solution rather than electrons in a metal. Biological systems also use electrical energy. For example, hydrogen ions, electrons, or metal ions may be more concentrated on side of a membrane than the other, setting up an electrical potential that can be used to transmit nerve impulses, move muscles, and transport materials.
Specific examples of electrical energy include:
The SI unit of potential difference or voltage is the volt (V). This is the potential difference between two points on a conductor carrying 1 ampere of current with power of 1 watt. However, several units are found in electricity, including:
|
Unit |
Symbol |
Quantity |
|
Volt |
V |
Potential difference, voltage (V), electromotive force (E) |
|
Ampere (amp) |
A |
Electric current (I) |
|
Ohm |
Ω |
Resistance (R) |
|
Watt |
W |
Electric power (P) |
|
Farad |
F |
Capacitance (C) |
|
Henry |
H |
Inductance (L) |
|
Coulomb |
C |
Electric charge (Q) |
|
Joule |
J |
Energy (E) |
|
Kilowatt-hour |
kWh |
Energy (E) |
|
Hertz |
Hz |
Frequency f) |
Always remember, a moving charged particle, whether it be a proton, electron, or ion, generates a magnetic field. Similarly, changing a magnetic field induces an electric current in a conductor (e.g., a wire). Thus, scientists who study electricity typically refer to it as electromagnetism because electricity and magnetism are connected to each other.