Electrostatic Charge Distribution (Charge Sensor)

Transcription

1 65 Electrostatic Charge Distribution (Charge Sensor) E&M: Electrostatic charge distribution Equipment List DataStudio file: 65 Charge Distribution.ds Qty Items Part Numbers 1 PASCO Interface (for one sensor) 1 Charge Sensor CI Charge Producers and Proof Planes ES-9057A 1 Faraday Ice Pail ES-9024A 1 Conductive Spheres (set of 2) ES-9059B 1 Electrostatics Voltage Source ES-9077 Introduction The purpose of this activity is to investigate electric charge distribution on a conductive sphere. Use a charge sensor, proof plane, Faraday Ice Pail, and the DataStudio software to record and plot the distribution of charge on the sphere. Background Like electric charges repel and unlike charges attract. The distribution of electric charge on the surface of an object illustrates this principle. If electric charge is transferred to an object that is electrically neutral, the transferred charge will tend to distribute itself evenly over the surface of the object IF the surface is conductive and allows the charges to move freely. The transferred electric charges repel each other and move as far from each other as possible. However, if the surface is non-conductive, the charges cannot move as freely and won t distribute evenly. The arrangement of charges in a non-conductive surface tends to attract or hold the transferred charges to that part of the object where they were transferred. Prediction Will the charge distribution on a conductive sphere be uniform or not? e and a d) decompressor e this picture. SAFETY REMINDER Follow directions for using the equipment. Setup 1. Set up the PASCO Interface and the computer and start DataStudio. 2. Connect the Charge Sensor to the interface. Set the GAIN switch to Open the DataStudio file: 65 Distribution.ds The file opens with a Table display of Location on Sphere and Charge. It also has a graph display and a meter display. The sample rate is set at 10 Hz. PASCO of 5

2 65 Electrostatic Charge Distribution Physics Experiment Manual Connect the alligator clips of the sensor s cable assembly to the inner and outer baskets of the Faraday Ice Pail. 5. Connect the Electrostatic Voltage Source to a Conductive Sphere. Attach the spade plug end of the cable to the sphere and put the banana plug end into the V jack on the voltage source. 6. Plug a second cable into the COM jack on the voltage source, but don t connect it to anything. Preparing to Record Data Before starting any experiment using the Faraday Ice Pail, the pail must be momentarily grounded. To ground the pail, touch the inner pail and the shield at the same time with the finger of one hand. Procedure Measure the Charge at Several Locations on the Sphere NOTE: Have one person handle the apparatus and a second person handle the computer. 1. Ground the Ice Pail and press the ZERO button on the Charge Sensor to discharge the sensor. 2. Click Start in DataStudio to start recording data. The Start button changes to Keep ( ). 3. Touch the top of the Conductive Sphere with the Proof Plane. Without touching the Ice Pail, lower the Proof Plane into the Ice Pail about halfway down. Watch the Table display. 4. Click Keep to record the charge for position Remove the Proof Plane and ground it by touching it to the end of the cable that is connected to COM on the voltage source. 6. Press ZERO on the Charge Sensor. 7. Touch one side of the Conductive Sphere with the Proof Plane and then lower the Proof Plane into the Ice Pail. Click Keep to record the charge for position Ground the Proof Plane and ZERO the Charge Sensor again. 9. Touch the opposite side of the sphere and again click Keep to record the charge on the Proof Plane of PASCO

3 Physics Experiment Manual 65 Electrostatic Charge Distribution 10. Repeat the process for two other places on the Conductive Sphere. 11. Click Stop ( ) to end data recording. Analyze Examine the graph of Charge versus Location. Use the Note tool in the software to indicate the location for each data point on the graph. Answer the questions in the Lab Report section. PASCO of 5

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5 Physics Experiment Manual 65 Electrostatic Charge Distribution Lab Report: Electrostatic Charge Distribution Name: Prediction Will the charge distribution on a conductive sphere be uniform or not? Data Sketch your graph of Charge and Location: Questions 1. How do the measurements of charge at the different locations on the sphere compare to each other? 2. What happens to the charge on the Conductive Sphere when it is connected to a source of charge such as the Electrostatic Voltage Source? 3. How do your results compare to your prediction? PASCO of 5