Definition and Characteristics of Conductors
– Conductors allow the flow of electric current.
– They can be objects or materials.
– Metals are common conductors.
– Electrons are the primary charge carriers in conductors.
– Insulators are non-conducting materials.
Resistance and Conductance
– Resistance depends on the material and dimensions of the conductor.
– Resistance is inversely proportional to the cross-sectional area.
– Resistance is directly proportional to the length of the conductor.
– Conductance is the reciprocal of resistance.
– Resistivity and conductivity are material properties.
Factors Affecting Conductivity
– Temperature affects the resistance of conductors.
– Expansion or contraction of the material changes the geometry and resistance.
– Phonons generated by temperature increase electron scattering and decrease current transfer.
– Alternating current (AC) and skin effect affect resistance.
– Proximity effect between conductors carrying AC current increases resistance.
Conductor Materials
– Conduction materials include metals, electrolytes, superconductors, semiconductors, plasmas, and some nonmetallic conductors.
– Copper is the international standard for electrical conductors.
– Silver is more conductive than copper but less practical due to cost.
– Aluminum is commonly used in power transmission and distribution.
– Aluminum has lower conductivity but is more cost-effective for large conductors.
Advantages and Disadvantages of Conductor Materials
– Copper is easy to connect and commonly used for light-gauge wires.
– Silver is used in specialized equipment and high-frequency applications.
– Aluminum is cost-effective for large conductors in power transmission.
– Aluminum wiring has disadvantages in mechanical and chemical properties.
– Organic compounds like hydrocarbons cannot conduct electricity.
Subtopic: Wire size
– Wires are measured by their cross-sectional area.
– Size is expressed in square millimeters in many countries.
– In North America, conductors are measured by American wire gauge for smaller ones.
– Circular mils are used for larger conductors.
– Wire sizes determine the amount of current a wire can carry.
Conductor ampacity
– Ampacity is the maximum amount of current a conductor can carry.
– Ampacity is related to the electrical resistance of the conductor.
– Lower-resistance conductors can carry higher currents.
– Resistance depends on the material and size of the conductor.
– Conductors with larger cross-sectional areas have less resistance.
Limitations of conductors
– Power lost to resistance can cause a conductor to melt.
– Most real-world conductors operate below this limit.
– Household wiring is usually insulated with PVC rated up to 60°C.
– Current in such wires must be limited to prevent fire risks.
– Other insulation materials like Teflon or fiberglass allow higher temperature operation.
Further reading
– Pioneering and historical books:
– William Henry Preece’s ‘On Electrical Conductors’ (1883).
– Oliver Heaviside’s ‘Electrical Papers’ (1894).
– Reference books:
– Annual Book of ASTM Standards: Electrical Conductors (published every year).
– IET Wiring Regulations by the Institution for Engineering and Technology.
External links
– BBC: Key Stage 2 Bitesize: Electrical Conductors.
– The discovery of conductors and insulators by Gray, Dufay, and Franklin.
– Wikimedia Commons: Media related to Electrical conductors. Source: https://en.wikipedia.org/wiki/Conductor_(material)
In physics and electrical engineering, a conductor is an object or type of material that allows the flow of charge (electric current) in one or more directions. Materials made of metal are common electrical conductors. The flow of negatively charged electrons generates electric current, positively charged holes, and positive or negative ions in some cases.
In order for current to flow within a closed electrical circuit, one charged particle does not need to travel from the component producing the current (the current source) to those consuming it (the loads). Instead, the charged particle simply needs to nudge its neighbor a finite amount, who will nudge its neighbor, and on and on until a particle is nudged into the consumer, thus powering it. Essentially what is occurring is a long chain of momentum transfer between mobile charge carriers; the Drude model of conduction describes this process more rigorously. This momentum transfer model makes metal an ideal choice for a conductor; metals, characteristically, possess a delocalized sea of electrons which gives the electrons enough mobility to collide and thus affect a momentum transfer.
As discussed above, electrons are the primary mover in metals; however, other devices such as the cationic electrolyte(s) of a battery, or the mobile protons of the proton conductor of a fuel cell rely on positive charge carriers. Insulators are non-conducting materials with few mobile charges that support only insignificant electric currents.
