Umair Gaines
Electrical terminology can be confusing, especially when speaking to professionals in the field. However, it is important to understand common electrical terms to communicate effectively with electricians and make informed decisions regarding electrical repairs, upgrades, and safety. This introduction will explain some of the most common electrical terms and their meanings, from basic concepts like AC current and ampere-hour to more specific terms like kilowatt-hour and load rejection. By the end, you should feel more confident discussing electrical systems and understanding the language of electricity.
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What You'll Learn
Dielectric strength and direct current
Dielectric strength is a measure of a material's ability to withstand electric stress without breaking down. When an electric field is applied, the material's atoms and molecules may polarize. If the field becomes too intense, it could lead to ionization, creating a conductive path and causing electrical breakdown. This is why materials with high dielectric strength are necessary for power lines and insulators—to withstand environmental conditions and constant stress from the electric field.
The dielectric strength of a material is independent of its configuration or the electrodes used to apply the electric field. However, in practice, the field strength at which breakdown occurs depends on the geometry of the dielectric and the electrodes, as well as the rate of increase of the electric field. Dielectric strength is typically measured using AC (alternating current) voltage, but it can also be tested using DC (direct current) voltage. The dielectric constant of a substance or material is a measure of its ability to store electrical energy, and this value decreases in the presence of a direct current voltage.
The dielectric strength of solid electrical insulating materials is determined according to ASTM standard procedure, which involves electrically stressing a specimen in a described electrode system by increasing the voltage until breakdown occurs. The test voltage is applied at a uniform rate. The theoretical dielectric strength of a material is an intrinsic property of the bulk material, and it is a crucial parameter in designing electrical systems and components. For example, in power distribution, dielectric strength is essential for preventing electrical breakdown and ensuring a stable power supply.
Dielectric materials are electrical insulators that can be polarized by an applied electric field. When placed in an electric field, no electric current flows within dielectric materials because they do not have loosely bound or free electrons. Instead, the positive and negative charges are displaced in opposite directions, creating an internal electric field that reduces the overall field within the dielectric. This phenomenon is known as polarization and is why dielectrics act as insulators, preventing the flow of electric current and reducing the risk of electrical shocks or fires.
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AC current and ammeters
An ammeter is an instrument used to measure the current in a circuit. The unit of measurement is "amps", or more precisely, amperes (A). To measure the electric current, an ammeter is connected in series with the circuit or component being measured. The ammeter's current sensitivity is determined by the amount of electric current required by the meter's coil to produce the required movement of the pointer.
There are various types of ammeters, including digital ammeters, which have no moving parts and can have accuracies better than 0.1 percent; and moving iron ammeters, which use a piece of iron that moves when acted upon by the electromagnetic force of a fixed coil of wire.
AC, or alternating current, is an electric current that periodically reverses direction and changes its magnitude continuously with time. This is in contrast to direct current (DC), which flows only in one direction. AC is the form of electric power delivered to businesses and residences and is used when consumers plug kitchen appliances, televisions, fans, and electric lamps into a wall socket. AC voltage may be increased or decreased with a transformer, allowing power to be transmitted through power lines efficiently at high voltage and then transformed to a lower, safer voltage for use.
AC is also used in applications such as guitar amplifiers, audio and radio signals, and electric generators, motors, and power distribution systems. AC generators, also known as alternators, do not require brushes and commutators to work, which makes them simpler in design than DC generators.
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Ground fault and grounding
A ground fault is an inadvertent contact between an energised conductor and the ground or a grounded equipment frame. It occurs when electricity takes an unplanned path to the ground, causing a drastic increase in the current and leading to a tripped breaker. This can happen when a hot wire comes into contact with either the grounding wire or a grounded part of the system, such as a metal electrical box.
Ground faults can be caused by damaged appliances, incorrect wiring, worn wire insulation, or overloaded circuits. They are particularly dangerous in areas with high moisture, such as bathrooms or garages, as water is a conductor of electricity and can move the electric current extremely quickly, increasing the risk of electrical shock. Other potential causes include pest damage to the electrical system, decayed insulation, and loose connections in the electric service panel or fuse box.
To prevent ground faults, it is important to ensure proper electrical grounding and earthing. This involves connecting all electrical equipment, including outlets, switches, and metal boxes, to a grounding wire that is connected to the earth. GFCI (ground fault circuit interrupter) outlets and circuit breakers can also be used in high-risk areas to monitor the flow of electrical current and automatically shut off the power in case of an imbalance, providing protection against electrical shock and reducing the risk of property damage and injury.
Additionally, regular inspection and maintenance of electrical systems are crucial in preventing ground faults. This includes identifying potential issues such as damaged insulation, incorrect wiring, or frayed cords, and taking proactive steps to address them. It is recommended to bring in an electrician or electrical engineer for preventative maintenance and to ensure that electrical systems are properly wired and functioning.
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Amplitude and analog
Amplitude is defined as the vertical distance from the highest to the lowest peak during one electrical wave. It is typically measured in milliamperes (mA). Current amplitude is also referred to as magnitude or intensity. Increasing the amplitude induces a stronger force of muscle contraction by recruiting additional muscle fibres at greater distances from the electrodes.
In the context of electricity, voltage or current is often referred to as the amount of electricity in a load, like a resistor (R ohms). However, the power of the electricity in a resistor is the current-squared times R (watts), or the voltage-squared divided by R (watts). Therefore, current or voltage is considered the amplitude, and the power is measured in watts.
Peak-to-peak amplitude is the change between the highest and lowest amplitude values. This is a common way of specifying amplitude, but other measures, such as root mean square (RMS) amplitude, are sometimes more appropriate. RMS amplitude is used especially in electrical engineering and is defined as the square root of the mean over time of the square of the vertical distance of the graph from the rest state.
Analog or analogue refers to electronic communication sent as signals of varying frequency. Analog signals are time-varying and are generally bound to a range, such as +12V to -12V. Within this continuous range, there is an infinite number of values. Analog signals use properties of the medium, such as electricity moving through a wire, to convey information. The voltage, current, or frequency of the signal may be varied to represent the information.
Analog methods allow equipment to handle information that continuously changes, such as voltage, current, and waves. Analog signals are often used to respond to changes in light, sound, temperature, position, pressure, or other physical phenomena. When plotted on a voltage vs. time graph, an analog signal should form a smooth and continuous curve without any discrete value changes.
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Resistance and resistors
Resistance is a measure of the opposition to the flow of current in an electrical circuit. It is influenced by the material's properties, length, cross-sectional area, and temperature. All materials resist current flow to some degree, but some materials, known as conductors, offer very little resistance, allowing electrons to move easily. Examples of conductors include copper and aluminium. On the other hand, insulators are materials that have high resistance and restrict the flow of electrons. Examples of insulators include rubber, paper, glass, wood, and plastic.
The electrical resistance of an object is measured in ohms (Ω), which is named after German physicist Georg Simon Ohm. The higher the resistance, the lower the current flow, and vice versa. Resistance can be measured using a digital multimeter or an ohmmeter.
Resistance is an important concept in electrical circuits, and this is where resistors come in. Resistors are passive electrical components made of materials that resist the flow of electricity as it passes through them, allowing them to control the flow of current throughout a circuit. They are commonly used in electronic circuits and are essential for ensuring that current flows at the appropriate level.
There are different types of resistors, including fixed resistors and variable resistors. Carbon-film resistors and metal-film resistors are examples of fixed resistors, which have fixed resistance values. Variable resistors, on the other hand, have resistance values that can be changed. Potentiometers are a type of variable resistor used to fine-tune voltage and current. Resistors can be connected in series or in parallel within a circuit. When connected in series, the current through each resistor is the same, and the equivalent resistance is equal to the sum of the individual resistors. In parallel connections, the voltage across each resistor is the same, and the inverse of the equivalent resistance is equal to the sum of the inverse values of the parallel resistors.
Resistors have a variety of applications, including limiting electric current, voltage division, heat generation, and gain control. They are commercially available with resistance values over a wide range. For example, they can be used as electric brakes in trains or in small electronic devices.
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Frequently asked questions
AC stands for Alternating Current, which is an electric current that changes direction many times a second.
A ground fault is a connection between a conductor of an electrical circuit and a conductor that usually does not carry a current. This conductor is called an ungrounded conductor.
A capacitor is a device that stores electrical energy. It is often used to filter out voltage spikes.
A diode is a device that only allows the flow of current in one direction. Current can flow when there is a positive anode and a negative cathode.
The term 'code' refers to the National Electrical Code (NEC). The NEC was established by the National Fire Protection Association (NFPA) in 1897 and its rules and standards are updated every three years.
