The Wiedemann-Franz Law Asaf Rozen, Alexander Palevski, Eli Raz The - - PowerPoint PPT Presentation

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The Wiedemann-Franz Law Asaf Rozen, Alexander Palevski, Eli Raz The - - PowerPoint PPT Presentation

Jun 12, 2023 109 likes •282 views

The Wiedemann-Franz Law Asaf Rozen, Alexander Palevski, Eli Raz The Wiedemann-Franz Law Heat and electrical transport involve free electrons 2 = 2 = = 2.44 10 8 2 3

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SLIDE 1

The Wiedemann-Franz Law

Asaf Rozen, Alexander Palevski, Eli Raz

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SLIDE 2

The Wiedemann-Franz Law

𝑀 = 𝜆 𝜏𝑈 = 𝜌2 3 𝑙𝐶 𝑓

2

= 2.44 ⋅ 10−8 𝑋𝛻 𝐿2

𝜆 𝜏

  • Heat and electrical transport involve free electrons
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SLIDE 3

The Wiedemann-Franz Law

  • Discovered in 1853

by Gustav Wiedemann and Rudolph Franz

  • Broadly used in modern

solid state physics

Crossno, J., Shi, J. K., Wang, K., Liu, X., Harzheim, A., Lucas, A., ... & Ohki, T. A. (2016). Observation of the Dirac fluid and the breakdown of the Wiedemann- Franz law in graphene. Science, 351(6277), 1058- 1061.

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SLIDE 4

Parts Of The Experiment

  • Part A – Electric conductivity (𝜏) of various metals.
  • Part B – Thermal conductivity (𝜆) of Copper.
  • Part C – Measure heat capacity (𝑑𝑞) and heat loss.
  • Part D – Measure the relative 𝜆 of different metals.
  • Part E – Discover the Wiedemann-Franz law.
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SLIDE 5

Equipment

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SLIDE 6

Part A – Electrical conductivy (𝜏)

  • Aluminum, Brass and

Copper tubes

  • Small magnet falls at a

constant speed

Top View

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SLIDE 7

Part B – Thermal conductivity (𝜆)

  • Power on one side,

Reservoir on the other

Heat reservoir Position [m] Temperature [C] Heater

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SLIDE 8

Part B – Thermal conductivity (𝜆)

Heat Reservoir Isolated Rod Readout Box

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SLIDE 9

Part B – Thermal conductivity (𝜆)

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SLIDE 10

Part C – Measure Heat Capacity And Heat Loss To Correct 𝜆

Heat reservoir Heater

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SLIDE 11

Part C – Measure Heat Capacity And Heat Loss To Correct 𝜆

Heat reservoir Heater

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SLIDE 12

Part C – Measure Heat Capacity And Heat Loss To Correct 𝜆

  • The rod is not at steady

state

  • There is heat loss to the

environment

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SLIDE 13

Part C – Measure Heat Capacity And Heat Loss To Correct 𝜆

  • The rod is not at steady

state

  • There is heat loss to the

environment

  • We use cooling-

heating-cooling cycle

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SLIDE 14

Part D – Measure The Relative 𝜆 Of Different Metals

  • Using alternating

material rod

  • Get accurate relative

thermal conductivity

  • Using the knowledge

from part C to correct results

Heat reservoir

Heat reservoir

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SLIDE 15

Part E – Discover The Wiedemann-Franz Law

Acknowledgments – Roy Beck- Barkai, Yoram Dagan