# Test and Measurement World

## Test and Measurement World Terminology Section

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## Seebeck Effect vs Peltier Effect vs Thomson Effect | Difference between Seebeck Effect Peltier Effect Thomson Effect

This page compares Seebeck Effect vs Peltier Effect vs Thomson Effect and mentions difference between Seebeck Effect, Peltier Effect and Thomson Effect.

The thermocouple is a temperature measuring device which works based on principles of following effects.

### Seebeck Effect

When the junctions of two different metals are maintained at different temperatures, the emf is produced in the circuit. This is known as "Seebeck Effect".

As shown in the figure-1, the conductor-1 is maintained at 'T+ΔT' temperature and conductor-2 is maintained at temperature 'T'. Since the junctions are maintained at different tempeartures, the emf "U" flows across the circuit.

The magnitude of the emf V produced between the two junctions depends on the material and on the temperature ΔT12 through the linear relationship defining the Seebeck coefficient S for the material
➨ ΔV = S * ΔT12

### Peltier Effect

Whenever current passes through the circuit of two dissimilar conductors, depending on the current direction, either heat is absorbed or released at the junction of the conductors. This is called as "Peltier Effect".

### Thomson Effect

Heat is absorbed or produced when the current flows in material with a certain temperature gradient. The heat is proportional to both the electric current and the temperature gradient. This is called as "Thomson Effect".

The thermoelectric effect is the direct conversion of heat differentials to electric voltage and vice versa. The good thermoelectric materials should possess large seebeck coefficients, high electrical conductivity and low thermal conductivity. The examples of such materials are Bi2Te3, PbTe, SiGe and Bi-Sb.