AQA ยท A level Physics

Graphene superconductivity A-level Physics challenge

Can you get 100%? Use layered graphene in a strong magnetic field to test zero resistivity, electrical power loss and scientific evidence.

Read about superconductivity in layered graphene

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Question

8 marks

Answer all parts. Show your working and give units where appropriate.

1(a)

State what is meant by superconductivity and the critical temperature of a superconductor.

[2 marks]

1(b)

A graphene device carries current 25 A. In its normal state its resistance is 0.080 ohm. Calculate the electrical power transferred to thermal energy in the normal state and state the corresponding value in an ideal superconducting state.

[3 marks]

1(c)

In many superconductors a strong magnetic field breaks the electron-pairing state. In this experiment a zero-resistance state survived up to 8.5 T and became stronger over part of the field range. Explain why this result challenges a conventional pairing model but does not by itself prove a particular alternative mechanism.

[3 marks]

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