Thermoelectric phenomena – emf in a single homogeneous wire Which effect relates the electromotive force (emf) developed in a single homogeneous conductor to the temperature difference along its length?

Introduction / Context:
Thermoelectric effects describe the coupling between heat flow and electric potential in conductors and junctions. Properly distinguishing Seebeck, Peltier, and Thomson effects is foundational for instrumentation and solid-state thermal management.

Given Data / Assumptions:

• Only a single homogeneous wire (no dissimilar junctions).
• A temperature gradient exists along the conductor.
• We seek the named effect directly linking emf and temperature gradient in that wire.

Concept / Approach:
The Seebeck effect refers to an emf generated in a circuit of two dissimilar conductors when their junctions are at different temperatures. The Peltier effect refers to heating or cooling at a junction when current passes. The Thomson effect is the emf (and reversible heat) produced along a single homogeneous conductor that has a temperature gradient and carries current; it directly relates emf to temperature difference along the wire itself.

Step-by-Step Solution:

Verification / Alternative check:
Textbook summaries: Seebeck → two metals, Peltier → junction heating/cooling, Thomson → single conductor with gradient. This matches the problem statement precisely.

Why Other Options Are Wrong:

• Peltier: Involves junctions of dissimilar materials and current flow.
• Seebeck: Requires a closed loop of two different conductors and two junction temperatures.
• None of these: Incorrect because Thomson is the proper effect.

Common Pitfalls:
Confusing Seebeck (two metals) with Thomson (single metal). Remember: Seebeck measures junction emf; Thomson is distributed along the conductor with temperature gradient.

Final Answer:
Thomson effect