Question

Assertion (A): Thomson effect is due to diffusion of free electrons in an unequally heated metal
Reason (R): Thomson effect takes place throughout the metal

• A. Both A and R are true and R is correct explanation of A
• B. Both A and R are true and R is not correct explanation of A
• C. A is true R is false
• D. A is false R is true.

Answer 1

Answer: (B)

Both A and R are true and R is not correct explanation of A

Thomson effect is due to diffusion of free electrons in an unequally heated metal but this diffusion does not take place throughout the metal.

Free Electron Theory of Metals:

Thomson effect is explained with the help of the free electron theory of metals. The theory explains that there exists different electron densities in different parts of unequally heated metals and the energy of free electrons in the hotter portion are higher compared to those of the colder portion.

Hence, the electron density remains higher at the lower temperature than that in the higher temperature region thus causing an emf to act from the colder region to hotter region. This produces absorption or evolution of energy which is Thomson effect.

Thus, we conclude that Thomson effect does not take place throughout the metal.