1. Charge It! Ground Lead: Keeps zero charge on cage. Ground Plane: Serves as a zero charge reference. Cage: Shields the pail from outside charges (like nearby hands) Base: Insulates cage & pail from ground plane To Charge Sensor Pail: THIS IS KEY! A charged object inside but not touching the pail induces the opposite charge on the inner wall and the same charge on the outer wall; which can be measured by the charge sensor.

2. Charge It! EXERCISE 1: Simple charge measurement The “wands” with plastic disks at the end are called “charge separators”. When rubbed together, one becomes positive (white nylon) and the other negative (gray PVC). Basic procedure: Connect the pail, cage and ground plane as shown previously. Don the wrist strap and connect it to the ground plane. Press “Reset”, which discharges the sensor and the pail. Rub the separators together. Start data collection and insert one disk into the pail (without touching) and hold for a couple seconds. Remove the separator.

3. Charge It! Basic procedure (cont.): Repeat the sequence with the other charge separator, and then with both separators at the same time. Examine the data graph and record the following: (1) charge of first separator, (2) charge with no separator, (3) charge with second separator, and (4) charge with both separators. Comment on whether the measurements agree with your expectations. You may need to practice a few times so you can do all three parts in sequence smoothly! Remove any remaining charge from the separators by moistening the small cotton cloth and touching it to the separator surfaces.

4. EXERCISE 2: Triboelectric Table You will now try to figure out what materials are best and worst at transferring charge by friction (triboelectricity). Use the same procedure as in Exercise 1, except use the different cloths and rods as charge separators. 4 insulating rods: clear acrylic, hollow polyvinyl chloride, white nylon and maple wood 4 cloths: blue silk, gray wool, patterned cotton and polyester felt Record all your measurements. Then list the rods from strongest negative to strongest positive. Do the same for the cloths. Charge It! It should be possible to make a combined list of rods & cloths — but I haven’t figured that one out yet.

5. Charge It! EXERCISE 3: Induction We’ll probably do this in class — but in case we don’t … Rub the disk charge separators, and insert the white one into the pail. Record the charge. (Should be positive.) While the separator is still in the pail, ground the pail by touching it. Record the charge. (Should be about zero.) Remove your finger from the pail & record the charge. (Still zero.) Now, remove the charge separator, and record the charge. (Should be negative and similar magnitude to original reading.)

6. Charge It! EXERCISE 3 (cont.): Induction Here’s what happened: When you inserted the separator originally, you induced a charge on the pail because the separator repelled like charges from the inner surface and pushed them to the outer surface where they could be measured by the sensor. When you touched the pail, negative charge from the ground plane was attracted to the positive charge on the pail, so the net charge on the pail is zero. When you take your finger away, the negative charges are trapped on the pail, and still cancel the positive charge on the separator. When the separator is removed, the positive charge induced on the pail also vanishes, leaving behind the stranded negative charge. DRAW A CARTOON ILLUSTRATING THIS PROCESS. Small print: The sensor is actually measuring the voltage difference between the cage and the pail, which is determined only by the charge on the outside of the pail.

7. Charge It! EXERCISE 4: Conduction Rub the disk charge separators, and insert the white one into the pail — and rub it along the inner wall, and then remove the separator. Record the charge. Why did the charge remain after the separator was removed from the pail? Check to see if the charge ACTUALLY left the separator by grounding and resetting the pail, and re-inserting the separator. Record the charge. Does the result indicate that charge leaves the separator when it contacts the pail? Repeat the procedure with the other charge separator.