Umair Gaines
Electrical terminology can be confusing, especially when speaking to an electrician, but it is important to know some basic terms for safety and to help troubleshoot simple problems. Some common electrical terms include outlet, which refers to any location in a circuit that supplies electricity, and code, which refers to the National Electrical Code (NEC), a set of rules and standards established by the National Fire Protection Association (NFPA) in 1897. Other terms relate to specific electrical components and their functions, such as diode, which allows current to flow in only one direction, and ampere-hour (Ah), which measures battery capacity. Understanding these terms can help you identify issues and take appropriate action to avoid hazards.
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What You'll Learn
AC and DC Current
In electrical terms, AC and DC refer to alternating current and direct current respectively. They are the two methods of electric current.
Direct current is a method in which electricity always flows in a certain direction, in a single direction with consistent voltage. It is obtained from batteries, solar cells, and fuel cells. The voltage is always constant, and the electricity flows in a certain direction. DC is commonly found in batteries, electronic devices, and solar panels, where a stable, unidirectional current is required for effective operation. DC is used to power smartphones, notebooks, earbuds, and other portable devices, as well as home appliances such as TVs, cameras, and gaming consoles.
Alternating current, on the other hand, is a method in which the positive and negative sides are constantly switched periodically and the direction of the flow of electricity changes accordingly. It is obtained from a generator or outlet, and the electricity produced at power plants and sent to homes is transmitted as alternating current. In alternating current, the voltage periodically changes from positive to negative and the direction of the current also periodically changes. AC is the most commonly used and most preferred electric power for household equipment, office, and buildings. It is also used to produce generators, motors, and power distribution systems. AC is also easier to transmit over long distances and can be converted to different voltages using transformers.
In terms of application, AC power is more suitable for larger power generation and distribution, while DC power has a smaller range of use cases, focusing more on low voltage and low current applications like electronic devices.
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Ammeters and Ohmmeters
An ammeter is a device used to measure the electric current in a circuit. The name is an abbreviation of "ampere meter", as the current is measured in amperes (A). Ammeters are usually connected in series with the circuit to be measured and have low resistance so that they do not cause a significant voltage drop.
There are various types of ammeters, including the moving-coil ammeter and the moving-iron ammeter. The former works on direct current only, while the latter, invented by Austrian engineer Friedrich Drexler in 1884, responds to both direct and alternating currents. Integrating ammeters sum the current over time, giving the product of current and time, which is proportional to the electrical charge transferred. Picoammeters, meanwhile, are used to measure very low electric currents, usually from the picoampere range to the upper milliampere range.
An ohmmeter, on the other hand, is a device used to measure the resistance of a resistor in an electrical circuit. The official unit of measurement for electrical resistance is ohms. Ohmmeters form circuits by themselves and therefore cannot be used within an assembled circuit. They must have their own power source for testing. A more accurate type of ohmmeter has an electronic circuit that passes a constant current through the resistance and another circuit that measures the voltage across the resistance. These measurements are then digitised and processed to offer the user a reading of the resistance value.
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Capacitors and Resistors
A capacitor is a device that stores electrical energy. It does this by accumulating electric charges on two closely spaced surfaces that are insulated from each other. The simplest design for a capacitor is a parallel plate, which consists of two metal plates with a gap between them. This gap can be a vacuum or filled with an insulating material known as a dielectric. The ability of a capacitor to store charges is known as capacitance. The term capacitor was originally known as a condenser, which is still used in high-power applications.
Capacitors are widely used as parts of electrical circuits in many common electrical devices. They are particularly useful as filters to divert spurious electric signals and prevent damage to sensitive components and circuits caused by electric surges. Capacitors are also used in digital circuits to store information in large computer memories to prevent data loss during a momentary power failure. Supercapacitors are capacitors with high capacitance that can store large amounts of energy and are used in electric cars, regenerative braking, and industrial electrical motors.
A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. Resistors are used to reduce current flow, adjust signal levels, divide voltages, bias active elements, and terminate transmission lines. The main purpose of a resistor is to reduce current flow and lower the voltage in any particular portion of the circuit. Resistors are made of copper wires that are coiled around a ceramic rod and coated with insulating paint. The SI unit of a resistor is Ohm.
There are two main types of resistors: fixed and variable. Fixed resistors have a specific value that cannot be changed, whereas variable resistors do not have a specific value and can be adjusted with a dial, knob, or screw. Variable resistors are often used in radio receivers for controlling volume and tone. Resistors may also be characterised according to their form factor, which refers to the size of the device and the position of its terminals.
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Diode and Electrolyte
A diode is a two-terminal electronic component that conducts electricity primarily in one direction. It has high resistance on one end and low resistance on the other. Diodes are used to protect circuits by limiting voltage and to transform AC into DC. They are essential to modern electrical systems, controlling the flow and direction of current.
Diodes are made from semiconductor materials like silicon and germanium. They are represented in circuit diagrams by a triangle with a line across one vertex. The most common type of diode uses a p-n junction, where one material (n) in which electrons are charge carriers, abuts a second material (p) in which holes (places depleted of electrons) are positively charged. When a diode allows current flow, it is forward-biased. When it is reverse-biased, it acts as an insulator.
Light-emitting diodes (LEDs) are p-n junctions that emit light when a current flows through them. LEDs are used in scoreboards, CD drives, DVDs, and laser devices. Photodiodes are used in sensors, solar cells, and photometers. They can identify even a small amount of current flow resulting from light and can also be used to generate electricity.
An electrolyte is a substance that conducts electricity through the movement of ions, but not through the movement of electrons. Electrolytes are substances that have a natural positive or negative electrical charge when dissolved in water. The most familiar electrolytes are acids, bases, and salts, which ionize when dissolved in solvents like water or alcohol. Many salts, such as sodium chloride, behave as electrolytes when melted, even in the absence of a solvent.
Electrolytes are essential in physiology, with the primary ions of electrolytes being sodium, potassium, calcium, magnesium, chloride, hydrogen phosphate, and hydrogen carbonate. Electrolyte balance is critical for nerve and muscle function, as well as maintaining fluid balance and blood pressure control. Electrolyte replacement is necessary for individuals with prolonged vomiting or diarrhea, and for athletes who lose electrolytes through sweating.
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Semiconductors and Conductors
The electrical conductivity of a material determines whether it is classified as a conductor, insulator, or semiconductor. Conductors are materials that allow electricity, heat, or sound to flow through them easily. They have high electrical conductivity and low electrical resistivity. Metals are good examples of conductors and are commonly used in everyday electrical equipment. On the other hand, insulators are materials that do not conduct electricity, exhibiting low conductivity and high electrical resistivity. They prevent the flow of energy, such as electricity, heat, or sound, between objects.
Semiconductors, as the name suggests, are materials with electrical conductivity values between conductors and insulators. They can act as conductors or insulators depending on certain factors, and this unique property makes them excellent for controlling electrical current. Semiconductors can be compounds, such as gallium arsenide, or pure elements, such as germanium or silicon. Their conductivity can be altered by "doping" or adding impurities to their crystal structure. The behaviour of charge carriers at these junctions forms the basis of diodes, transistors, and most modern electronics.
The difference in charge carrier density distinguishes conductors from semiconductors. In conductors, the valence band, which is the highest energy band occupied by electrons, is partially filled, allowing electrons to move freely under the influence of an electric field. In contrast, semiconductors have their valence bands filled at absolute zero, and their band gap is smaller than that of insulators. When the temperature increases, more electrons gain enough energy to move into the conduction band, increasing the conductivity of the semiconductor.
At room temperature, a significant number of electrons in semiconductors can be excited to cross the band gap, but a pure semiconductor is neither a good conductor nor a good insulator. Semiconductors are essential in modern technology, from simple clocks to advanced supersonic aircraft, and they are the foundation for computers and other electronic devices. Their ability to control electrical current makes them valuable in clean energy initiatives, such as solar panels, wind power, and electric cars.
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Frequently asked questions
"AC" stands for alternating current. This is an electric current that changes direction many times a second at regular intervals.
"DC" stands for direct current. This is an electric current that flows in only one direction.
"Ohm" is the standard unit for measuring resistance to the flow of an electrical current. It is represented by the Greek letter omega (Ω).
