Low Temperature Phenomena

Copper and Bulb

Copper has positive temperature coefficient; light bulb gets brighter when copper leads are dipped in liquid N2.

What it shows: 

Copper has a positive temperature coefficient (≈ 3.9×10-3 per ˚C), which means that its resistance drops with temperature. Here copper wire is immersed in liquid nitrogen (77˚K = -196˚C), decreasing its resistance (from room temperature) by almost a factor of 2, thus increasing the current flow though a circuit.

How it works: 

We have a coil of 30AWG copper wire...

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Jumping Ring

Shoot the ring through the roof after dipping it in liquid N2; Lenz's law induced EMF in metal ring.

What it shows: 

The induced current in a metal ring is dramatically increased by lowering the ring's temperature.

How it works: 

Here is an extension of the ...

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Meissner Effect

What it shows:

A superconducting material in the presence of an external magnetic field excludes that field from its interior. This is shown by levitating a magnet above a high-temperature superconductor.


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Lead Bell

Dull at room temperature, rings clearly after immersion in liquid nitrogen.

What it shows: 

A lead bell, dull sounding at room temperature, rings brightly when cooled to liquid nitrogen temperatures.

How it works: 

A lead bell at room temperature is dull in more ways than one. But its elasticity is temperature dependant, with an increase in elasticity as its temperature decreases. This increase in elastic modulus narrows the resonance response with frequency and increases the quality Q of the lead as...

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Everyday objects at low temperature

What it shows:

Mechanical properties of some materials change dramatically with temperature. These changes have entertaining effects on everyday objects by taking them from room temperature 300K to the temperature of liquid nitrogen 77K.

How it works:

Place your everyday objects in a dewar of liquid nitrogen for several minutes (at least until the LN2 stops boiling). Some examples to use:

1. Rubber gloves freeze solid and shatter on impact with floor.
2. Use a banana to hammer a nail into wood
3. Frozen...

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Change of Volume with State

CO2 and He balloons in liquid nitrogen.

What it shows:

Cooling a gas causes a proportional decrease in volume with the drop in absolute temperature. A gas such as helium, which remains close to ideal at low temperatures, shows a four-fold decrease in volume when taken from room temperature 330K to liquid nitrogen temperature, 77K. Carbon dioxide however, sublimes at 194.5K, so is solid at 77K. Oxygen liquefies at 90K (S.T.P.). A qualitative demonstration of these effects can be shown with gas filled balloons.

How it works:...

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Ring Flinger Lenz's Law

What it shows:

A changing magnetic flux induces a current in a metal ring; the magnetic field due to this current opposes the primary field, repelling the ring and flinging it into the air. That's the simple "hand waving" explanation for the beginner student—a more accurate explanation follows.

How it really works:

The jumping ring is a vivid and popular demonstration of electromagnetic induction and is used to illustrate Faraday's and Lenz's laws. A conducting ring, placed over the ferromagnetic core of a solenoid, may levitate or...

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