3B Scientific Yi Bell - Manual

3
Operating instructions
3B SCIENTIFIC® PHYSICS
U30002 Yi bell
1/03 ALF
®
The Yi bell is used to demonstrate the relationship be-
tween temperature and oscillation damping.
1. Safety instructions
• Only use solid fuel (Esbit) in the students’ experi-
ment.
• In the demonstration experiment, do not saturate
the cloth with liquid fuel (methylated spirit).
• Exercise particular caution when igniting the fuel.
• Only ignite the fuel with matches.
• Do not touch the bell or burner during or after the
heating phase.
• Allow the bell to cool after completing the demon-
stration.
2. Description, technical data
This „bell of faith“ was copied from a 2-tone bell dis-
covered in 1978 in the grave of the Chinese marquis Yi
from the 5th century BC. It is cast from a newly devel-
oped copper-magnesium alloy and possesses a singu-
lar physical characteristic resulting from its special
shape and the effect of temperature on oscillation
damping. A curve of the energy decrement per period
is plotted against the temperature in Figure 1. The
change in the elastic characteristics of the alloy, (A
n
2 -
A
n+l
2)/A
n
2, expressed here as a percentage, is consider-
able from room temperature to approximately 100°C.
At room temperature, the bell only sounds dull and
wooden. However, if it is heated for several minutes
with an alcohol burner, it produces a beautiful tone.
Figure 2 shows the acoustic oscillations before and af-
ter the bell is heated.
The bell is stowed in a robust wooden box with a fabric
and velvet lining.
Ener
gy
decr
ement per period %
Temperature in °C
Figure 1
Graph of energy decrement per period as a function of temperature Figure 2
Change in the attenuation and frequency of the bell before and after
heating. Top: cold; bottom: hot