Wiktor Wise
Electric circuits are an essential part of our daily lives, powering everything from simple flashlights to complex computers. A basic understanding of the materials involved in these circuits is crucial to grasp how they function. Electric circuits are pathways for transmitting electric current, and they consist of several components, including energy sources like batteries or generators, devices that utilise the current, such as lamps or motors, and connecting wires or transmission lines. The materials used in these circuits can be broadly categorised into conductors, which facilitate the flow of electric charge, and insulators, which impede it. Conductive materials include metals, electrolytes, superconductors, semiconductors, and some non-metallic conductors like graphite, while insulators typically have low electron mobility and can be made of materials like plastic, rubber, or wood.
| Characteristics | Values |
|---|---|
| Materials used in electric circuits | Conductors, insulators, SRBP solder, copper strips, chip holder, socket, contacts, resistance, resin |
| Conductors | Silver, dirty water, concrete, metals, graphite, aluminium |
| Insulators | Glass, paper, resin, plastic, rubber, wood |
| Electric circuit | A path for transmitting electric current |
| Types of electric circuits | Direct-current circuit, alternating-current circuit, series circuit, parallel circuit |
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Conductors and insulators
Electric circuits are made up of conductors and insulators. Materials that conduct heat or electricity are known as conductors, and those that do not are called insulators. The relative mobility of electrons within a material is known as electric conductivity, and materials with high electron mobility are conductors, while those with low electron mobility are insulators. Conductors have a very low resistance to electrical current, while insulators have a very high resistance.
Conductors may appear solid, but any material composed of atoms contains mostly empty space. Electrons move uniformly through a conductor, pushing the electron ahead of it, causing all the electrons to move together as a group. This movement of electrons is what we call electricity or electric current. Silver is the best conductor, offering easier passage for electrons than any other material. Copper, gold, aluminium, and most other metals are also good conductors. Conductors can be used to cool or heat things down quickly, such as a metal saucepan transferring heat to food inside.
Insulators are used to protect us from the dangerous effects of electricity flowing through conductors. For example, electrical wires are wrapped in plastic, which is flexible and insulating. It prevents electricity from flowing out of the circuit. The rubber coating on wires is another example of an insulating material. Glass, paper, resin, wood, plastic, and many fabrics such as wool and cotton are good insulators.
Some materials can be both conductors and insulators depending on the conditions. For instance, glass is a good insulator at room temperature but becomes a conductor when heated to a very high temperature. Similarly, gases like air are normally insulating but become conductive when heated.
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Metals
The resistance of a conductor depends on the material it is made of, and its dimensions. For a given material, the resistance is inversely proportional to the cross-sectional area. For example, a thick copper wire has lower resistance than a thin copper wire. Copper is the international standard for electrical conductivity, and it is the most common choice for most light-gauge wires due to its high conductivity and ease of connection.
Temperature also has a significant effect on the efficacy of conductors. As the temperature increases, the number of phonons generated within the material increases. Phonons are small, harmonic kinetic movements of the atoms of the material, which disrupt the path of electrons, causing them to scatter. Most metals become poorer conductors when heated, and better conductors when cooled.
In an electric circuit, a conductor is connected to a device that gives energy to charged particles, such as a battery or generator, and a device that uses the current, such as a lamp or electric motor. Electricity requires a complete "loop" for the current to flow, which is called a closed circuit. When a metal object is touched with a free wire end, the bulb lights up because metals are conductors, creating a closed circuit.
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Circuits and current
Electric circuits are pathways for transmitting electric current. They are made up of a device that provides energy to charged particles, such as a battery or generator; devices that use this current, like lamps, electric motors, or computers; and connecting wires or transmission lines.
The flow of charged particles, or electric current, is made possible by materials that allow the movement of these particles, known as conductors. Conductors are typically materials with high electron mobility, often possessing a "delocalized sea of electrons", which allows for the transfer of momentum and the flow of current. Metals are the most common conductors, with silver being the best conductor, offering the easiest passage for electrons. Other conductors include electrolytes, superconductors, semiconductors, plasmas, and some non-metallic conductors like graphite and conductive polymers.
Insulators, on the other hand, are materials with low electron mobility that impede the flow of current. Examples of insulators include plastic, rubber, wood, and glass at room temperature. However, it's important to note that some materials can act as both conductors and insulators under different conditions. For instance, while glass is a good insulator at room temperature, it becomes a conductor when heated to very high temperatures.
Electric circuits can be either direct-current (DC) or alternating-current (AC) circuits. In a DC circuit, the current flows only in one direction, while in an AC circuit, the current pulsates back and forth many times a second, as seen in most household circuits. Circuits can also be series or parallel circuits. In a series circuit, the current follows a single path, while in a parallel circuit, the current divides into branches, with the voltage remaining the same across each branch.
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Resistors
Ohm's Law describes the relationship between voltage, resistance, and current. It can be used to calculate the resistor value needed for a specific application. For instance, if a max current of 100mA (0.1A) is needed with a supply of 5V and a minimum input tolerance of 3.5V, the resistor value should be calculated using Ohm's Law as 1.5V/0.1A = 15 ohms.
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Circuit boards
Printed circuit boards (PCBs) are found in practically all electrical devices. The choice of material for a PCB depends on the expected results and the application. The primary material used to fabricate PCBs is of immense importance as the performance and level of integration of the PCB depend completely on the chosen material.
There are two main categories of materials used in the production of PCBs: Thermosets and Thermoplastics. Thermosets have high melting points, but once exposed to a certain temperature and cured to a solid state, their components and physical properties become set. They include resins such as epoxy, polyimide, and aramid. Thermoplastics, on the other hand, have low melting points and can be shaped into nearly any mould or design. Thermoplastics are usually PTFE-based, which is a kind of plastic material that does not provide any resistance and is thus used for high-speed, high-frequency applications.
The three major types of materials used for fabrication of PCBs are FR-4, PTFE (Teflon), and metals such as copper, aluminium, and iron. FR-4 is the most commonly used material in PCBs. It is a glass-reinforced epoxy laminate sheet that is flame retardant and water-resistant. PTFE, or Teflon, is a plastic material that does not provide any resistance and is used for high-speed applications. Metal PCBs provide mechanical durability and have a longer product life.
Other materials used in PCB substrates include polyimide, which is used in flexible printed circuit boards (Flex-PCBs). Polyimide is lightweight, flexible, and resistant to high temperatures and most chemicals. Rogers material is another type of rigid substrate used in high-frequency, high-performance electronic applications. Metal-core PCBs (MCPCBs) use a metal base material, such as aluminium or copper, as the substrate instead of a traditional insulating material. MCPCBs offer improved thermal management and are suitable for applications that generate a lot of heat.
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Frequently asked questions
An electric circuit is a path for transmitting electric current. It includes a device that gives energy to the charged particles constituting the current, such as a battery or a generator; devices that use current, such as lamps, electric motors, or computers; and the connecting wires or transmission lines.
Electric circuits are made up of a variety of materials, including metals, electrolytes, superconductors, semiconductors, plasmas, and some non-metallic conductors like graphite and conductive polymers. The most common material is copper, which is used for its high conductivity and ease of connection by soldering or clamping.
A conductor is a material that allows the flow of electric charge (current). Metals are common electrical conductors due to their delocalized sea of electrons, which gives them high mobility. Insulators, on the other hand, are non-conducting materials with few mobile charges that support only insignificant electric currents. Examples of insulators include plastic, rubber, and wood.
Temperature has a significant effect on the efficacy of conductors. Materials may expand or contract with changes in temperature, altering their geometry and resistance characteristics. Additionally, an increase in temperature increases the number of phonons (lattice vibrations) within the material, disrupting the path of electrons and causing them to scatter.
