Conductometer, PIRA#

Location:

• Cabinet: Thermodynamics Cabinet

• Bay: (A4)

• Shelf: #1

(attachment photo showing the fully set up demonstration)

Description:

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Setup:

1. Install the burner gas tube with the gas source.
2. Make sure that you have the gas switch off and in the right pressure that you want before you turn it on.
3. Make sure that the conductometer has been assembled if not, do the following.
   • - Place the bottom disk, which has the threaded center hole, on a flat surface with the groove face upward. - Fit the brass and iron wire into the center grooves of the bottom disk, having approximately 3 inches of wire extending beyond end of the plate.

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• - Hold the two wires in place by pressing with one's fingers on the wires on each side of the disk. Locate the upper disk on top of the bottom disk, seeing that the grooves match. Thread the screw into disks partly so as to hold the wires in position and still allow space to slide the short wires into the outer grooves. - Slide the aluminum wire into the grooves near the brass wire, loosening screw slightly if necessary. Repeat with copper wire locating it in grooves nearest iron wire.

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• - Hold the two wires in place by pressing with one's fingers on the wires on each side of the disk. Locate the upper disk on top of the bottom disk, seeing that the grooves match. Thread the screw into disks partly so as to hold the wires in position and still allow space to slide the short wires into the outer grooves. - Slide the aluminum wire into the grooves near the brass wire, loosening screw slightly if necessary. Repeat with copper wire locating it in grooves nearest iron wire.

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• - The disk may be located by sliding along the center wires so that the wire ends are approximately the same distance from the disk periphery. A length of about 3 inches will suffice. Tighten center screw after checking that each wire is located correctly in its respective groove.

Cautions, Warnings, or Safety Concerns:

1. Beware of heated plate and wires.
2. It may take time to assemble the conductometer.

Demonstration: In operation, indicators in the form of a marble attached by bee wax onto the end of the wires should be used. The apparatus is held so that the burner is locate under the disk, avoiding having the flame touching the wires directly.

It will be seen that the indicator marbles will drop off in the order of the conductivity of the wires. Since the iron wire id the poorest conductor, the indicator ball will hold after the other three have dropped off. It is not necessary to heat further since the conductivity order has been established.

Theoretically, heat is the evidence of increased rate of vibration of the molecules of a substance. If one end of a rod is set into greater molecular vibration by heating, the vibrations will be transmitted along the rod until the whole rod reaches an even temperature. Since the rods conduct heat at different rates, the amount of heat transmitted to each end will vary and the indicator balls will drop off at different times. The order of conductivity of the tested metals is thus shown.

References:

1. Instructions for assembly and use of No. 1651 Conductometer. SARGENT-WELCH SCIENTIFIC COMPANY

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