Millikan Oil Drop Apparatus
Equipment
®
8
012-13093B
4.
Plug the included AC adapter into a receptacle (100 to 240 VAC) and connect the cable to the power jack on
the side of the LED light source..
5.
Bring the reticle into focus by turning the reticle focusing ring.
6.
View the focusing wire through the viewing scope and bring the wire into sharp focus by turning the droplet
focusing ring.
•
NOTE
: Viewing will be easier for experimenters who wear glasses if the viewing scope is focused without
using the glasses.
7.
Return the focusing wire to its storage location on the platform.
Functions of Controls
Ionization source lever
1.
When the lever is in the ionization
OFF
position, the ionization source
is rotated away from the area of the droplets, so virtually no alpha parti-
cles enter the area. In this position, the alpha source is shielded on all
sides.
2.
At the
ON
position, the ionization source is rotated toward the area of
the droplets and the area is exposed to the ionizing alpha particles from
the thorium-232.
3.
At the
Spray Droplet Position
, the chamber is vented by a small hole
that allows air to escape when oil droplets are being introduced to the
chamber.
Plate charging switch
The plate charging switch has three positions:
1.
TOP PLATE –: negative binding post is connected to the upper capacitor plate.
2.
TOP PLATE +: negative binding post is connected to the lower capacitor plate.
3.
PLATES GROUNDED: plates are disconnected from the high voltage supply and are electrically connected
to each other.
Adjusting and Measuring the Voltage
1.
Connect the high voltage DC power supply to the plate voltage connectors using banana plug patch cords.
2.
Adjust the voltage to deliver about 500 VDC. Use the digital multi meter to measure the voltage delivered to
the plate voltage connectors.
.
Check to make sure that the AC adapter is the correct voltage: 100, 117, 220, or 240 V.
Figure 8: Ionization source
lever settings
housing
ionization
ON
position
spray
droplet
position
ionization
OFF
position
ionization
lever
Measure the voltage at the plate voltage connectors and not across the capacitor plates.
There is a ten megaohm resistor in series with each capacitor plate to prevent electric shock.
