Charge Produced by Friction

Figure 1

In this experiment you will charge pairs of objects by rubbing them together. Some materials release electrons more easily than others. When you rub the two objects together, some electrons from one object are transferred to the second object. For example, when rubbing a piece of polyvinyl chloride (PVC) plastic with wool, you will find that the PVC gains electrons and so becomes negatively charged, while the wool becomes positively charged. This tells you that wool gives up electrons more readily than PVC. In this experiment, you will measure the charges on these object pairs using the Electrostatic Charge sensor.

einstein™Tablet+ with MiLAB or Android /iOS Tablet with MiLAB and einstein™LabMate Electrostatic Charge sensor Test leads with BNC connector Faraday ice pail Materials: Glass rod (Pyrex is best), ebonite rod, PVC plastic strip (or pipe), silk cloth, neoprene rubber glove, wool cloth Silk thread

1.

2.

Launch MiLAB ( ).

Connect the Electrostatic Charge sensor to one of the ports on the einstein™Tablet+ or einstein™LabMate.

3.

4.

Connect the test leads to the Electrostatic Charge sensor.

Make sure that only the Electrostatic Charge sensor is selected.

Program the sensor to log data according to the following setup: Electrostatic Charge Sensor

Charge, 25 nC (nC)

Set As Zero

ON

Rate:

10/sec

Duration:

2 Min

1.

Wrap the small woolen cloth around the end of the PVC plastic strip or the glass rod. Secure it tightly with the silk thread (see Figure 2).

2.

Figure 2 Short circuit the two leads of the Electrostatic charge sensor. To short circuit the sensor, connect the positive (red) and negative (black) leads.

3.

Tap Run (

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5.

Rub the woolen cloth along the length of a strip of PVC plastic (see Figure 2).

Lower the PVC plastic strip into the lower half of the inner cylinder of the Faraday pail and hold it suspended there, without allowing it to touch the pail (see Figure 1).

6.

Tap Stop (

) to stop collecting data.

7.

Tap Save (

) to save data.

8.

9.

10.

11.

Remove the strip from the Faraday pail.

Short circuit the two leads of the Electrostatic charge sensor.

Next, insert the woolen cloth into the pail and record the readings.

Repeat steps ‎3 to ‎8 with other pairs of materials, rubbing cloth against a strip or rod.

) to begin recording data.

1.

2.

What happens when you rub a woolen cloth against PVC plastic?

Are the objects that have been rubbed together always charged equally and opposite in charge, when you measure them? Explain.

Which of the pairs of materials that you have rubbed together give off electrons more easily?