Ball and ring; Plate with hole

Relevant Resource questions :

Concepts demonstrated :

• thermal expansion of solids

Equipment needed :

• Large lead support
• Trevelyan rocker
• bunsen burner and matches
• CCD camera

• Heat rocker and place on the cool lead support.

None.

Physics involved :

Rapid thermal expansion of the lead when heated tips the rocker so that the other edge makes closer contact with the lead. The process is repeated producing a rapid rocking motion and enough sound for a lecture theatre.

How to use the Demonstration :

• Ask the students what they think will happen when the hot head is placed on the cool lead.
• Perform the experiment showing that the head rocks back and forth.
• Ask the students to explain why the head rocks.

Things to do or add :

Other Comments :

• This experiment can be difficult to perform. Sometimes the head will not rock.