- Actuators
- Adapters
- Air Blowers
- Air Conditioners
- Air Curtains
- Air Purifiers
- Anemometers
- Axial fans
- Ball Valves
- Belimo
- Blowers
- Brackets
- Brass
- Brazing Rods
- Capacitors
- Carrier Parts
- Clamp Meters
- Cleaning Products
- Coatings
- Compressors
- Condensate Pumps
- Connectors
- Contactors
- Copper Capillary
- Copper Coils
- Copper Straight Tubes
- Copper Strainers
Positive Temperature Coefficient
Positive Temperature Coefficient
A Positive Temperature Coefficient (PTC) refers to a material property where the electrical resistance of the material increases as its temperature increases.
In simpler terms: hotter = more resistance; colder = less resistance.
Here is a breakdown of how it works, why it happens, and how it is used in engineering.
The Science: Why Does It Happen?
To understand PTC, look at what happens inside a typical conductor (like copper, aluminum, or gold) at an atomic level:
- At Low Temperatures: The atoms inside the metal lattice are relatively still. Free electrons can easily zip through the material with minimal interference, resulting in low electrical resistance.
- At High Temperatures: As heat is added, the atoms absorb thermal energy and begin to vibrate violently in place. This frantic vibration creates a “chaotic obstacle course” for the flowing electrons. The electrons collide with the vibrating atoms much more frequently, which slows them down—this restriction of flow is what we measure as increased resistance.
How does PTC apply to HVAC/R?
Most metals (Copper, Aluminum, Iron) and specialized PTC ceramics used in HVAC/R have a positive temperature coefficient. Higher internal insulation in these machines is key to longevity in extreme heat.
