Conducting Materials Quiz

Conducting materials

• Conductors allow electric current to flow with minimal resistance.
• Metals are key conductors:
  • Copper is widely used due to its high conductivity, good ductility, and corrosion resistance.
  • Aluminum is lighter and less expensive, often used for power transmission.
  • Silver is the most conductive but expensive, primarily used in high-frequency applications.
• Alloys are metal mixtures enhancing specific properties:
  • Constantan (copper-nickel) has low temperature coefficient of resistance, ideal for resistors and strain gauges.
  • Nichrome (nickel-chromium) has high resistivity and oxidation resistance, used in heating elements.
• Carbon-based materials are also conductive:
  • Graphite offers high conductivity and is used in electrodes, brushes, and as a lubricant.
  • Carbon nanotubes have exceptional conductivity and are used in nanotechnology and composite materials.
• Semiconductors conduct under specific conditions, like doping or light exposure.
  • Silicon and germanium are key semiconductor materials.
• Superconductors exhibit zero electrical resistance below a critical temperature.
  • Examples include niobium-titanium (NbTi) and yttrium-barium-copper oxide (YBCO).
  • Used for high efficiency applications like MRI magnets and high-speed data transfer.
• Ionic conductors conduct electricity through ion movement, found in batteries and fuel cells.

Metallic conduction theory

• Free electron theory explains electron behavior in metals.
• Assumptions:
  • Electrons in the outer energy levels are weakly bound, becoming free electrons.
  • Free electrons move freely within the metal lattice due to minimal potential barriers.
  • Thermal motion causes atoms to vibrate, impacting electron movement and creating resistance.
• Important aspects:
  • Electrical conductivity is high due to the abundance of free electrons.
  • Energy levels and Fermi level: Electrons occupy discrete energy levels, with the Fermi level representing the highest occupied level at absolute zero.
  • Band structure: Metals have a partially filled conduction band overlapping with the valence band, allowing easy electron movement.
  • Electrical resistivity arises from electron scattering by lattice imperfections and thermal vibrations.
• Limitations of the free electron model:
  • Most accurate for simple crystal structures and low temperatures.
  • Oversimplifies band structure interactions.
  • Doesn't account for anisotropic conductivity or specific behaviors of transition metals and alloys.

Variations of conductivity

• Temperature dependence:
  • Metals: Conductivity decreases with increasing temperature due to enhanced lattice vibrations scattering electrons.
  • Semiconductors: Conductivity increases with temperature due to electron promotion from the valence to conduction band.
• Composition dependence:
  • Metals: Alloy composition affects conductivity, impurities and phase changes can disrupt electron movement decreasing conductivity.
  • Semiconductors: Doping with impurities significantly alters conductivity.
  • Composite materials: Conductivity depends on the conductivity of both reinforcement and matrix materials.

General Electric

• Multinational conglomerate operating in various segments:
  • Aviation: engines, systems, and services
  • Power: energy products and services
  • Renewable Energy: wind, solar, and grid solutions
  • Healthcare: medical imaging and diagnostics
  • Capital: financial services
• Founded by Thomas Edison in 1892.
• Global reach with over 205,000 employees.
• Known for innovation and technological advancement, particularly in digital industrial technologies, renewable energy, and healthcare.
• Faced financial challenges in recent years, undergoing restructuring efforts and focusing on core businesses.
• A commitment to environmental and social responsibility, promoting sustainability and renewable energy solutions.

Materials for brushes, lamp filaments, fuses, and solder

• Brushes of electrical machines:
  • Carbon brushes are common due to their conductivity, low friction, and wear resistance.
  • Graphite is suitable for high-speed applications.
  • Metal graphite combines metal particles and graphite providing enhanced conductivity and wear resistance.
• Lamp filaments:
  • Tungsten is the primary material due to its high melting point and resistance to deformation at high temperatures.
  • Carbon filaments are occasionally used in specialized applications.
• Fuses:
  • Copper is widely used for its conductivity and safe current carrying ability.
  • Silver is used in high-performance fuses for lower resistance and higher conductivity.
  • Aluminum is used in larger fuses for cost-effectiveness and weight reduction.
• Solder:
  • Tin-Lead alloy (Sn-Pb) is traditional, offering good flow properties.
  • Lead-free alloys like Sn-Ag-Cu and Sn-Cu are used due to lead health and environmental concerns.
  • Silver solder contains more silver, providing higher joint strength used in plumbing and electrical connections.

Test your knowledge on conducting materials, including metals, alloys, and carbon-based materials. This quiz covers key properties and applications of conductors such as copper, aluminum, and graphite. Dive into the fascinating world of electrical conductivity and its essentials.