The Thomson effect is a thermoelectric phenomenon where heat is either absorbed or evolved when an electric current flows through a single, homogeneous conductor that has a temperature gradient along its length. This means if one part of the conductor is hotter than another and current passes through it, heat transfer occurs inside the conductor itself, in addition to the usual resistive heating

. Key points about the Thomson effect:

• It occurs in a single material with a temperature difference along its length.
• Heat can be absorbed or released depending on the direction of current and temperature gradient.
• It is one of the three reversible thermoelectric effects, alongside the Seebeck effect and the Peltier effect.
• The effect was predicted by William Thomson (Lord Kelvin) in the mid-19th century based on thermodynamic reasoning

• The Thomson coefficient quantifies the amount of heat generated or absorbed per unit length, per unit current, and per unit temperature gradient in the conductor

In practical terms, the Thomson effect is important in thermoelectric devices used for energy conversion, temperature sensing, and cooling technologies

. In summary, the Thomson effect describes heat transfer linked to electric current flowing through a conductor with a temperature gradient, distinct from heat generated by electrical resistance alone