A Superconductive Switch
When a superconductor is in the normal state the resistance to the flow
of current is quite high compared to the superconducting state. Because of
this, a simple resistance switch can be easily demonstrated.
- YBCO superconductive wire with attached leads
- 2 C batteries with holder
- 3 volt flash light bulb with holder
- liquid nitrogen
- dewar or styrofoam cup
- Connect superconductor, light bulb and batteries as shown in Figure (20).
- When the superconductor is at room temperature it is in the normal state
and will have high resistance.The bulb will not light.
- Place the superconductor into the liquid nitrogen. The bulb will light as
the resis tance decreases.
- Remove the superconductor from the liquid nitrogen. The bulb will begin
dim and eventually go out as the resistance increases.
Caution: This demonstration requires low-resistance contacts to the
superconductor.If the switch fails to provide change in light intensity, repeat
contact construction as described in the Preparation of the 1-2-3 Superconducting Pellet section. The superconductor may well
need an anneal.
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