Thermoelectric phenomena – heat absorption/evolution at junctions The relation connecting heat absorbed or evolved at a thermocouple junction with the electric current in the circuit is known as which thermoelectric effect?

Introduction / Context:
Thermoelectricity involves three closely related effects: Seebeck, Peltier, and Thomson. Distinguishing them is crucial for understanding thermocouple operation, active cooling devices, and temperature-gradient energy flows.

Given Data / Assumptions:

• Peltier effect concerns heat exchange at a junction when an electric current passes.
• Seebeck effect concerns electromotive force generated by junctions at different temperatures.
• Thomson effect concerns heat absorption/evolution along a conductor with a temperature gradient and current.

Concept / Approach:
The question explicitly mentions heat absorption/evolution at the junctions related to current flow. This is the Peltier effect: Q̇ = Π I at the junction, where Π is the Peltier coefficient specific to the junction pair and I is current. Seebeck relates voltage to temperature difference (E = S ΔT), and Thomson relates distributed heating/cooling to current in a temperature gradient along a single conductor.

Step-by-Step Solution:

Verification / Alternative check:
Thermoelectric coolers (TEC) exploit the Peltier effect by driving DC current through junctions to pump heat.

Why Other Options Are Wrong:

• Seebeck: Voltage due to temperature difference, not junction heat vs current.
• Thomson: Distributed along a conductor with gradient, not at the junction.
• None: Incorrect because the Peltier effect exactly matches the description.

Common Pitfalls:
Mixing up which effect produces EMF (Seebeck) versus which moves heat under current (Peltier).

Final Answer:
Peltier