7. One at a time, insert the Charge Producer (one glass, one dark plastic, see image below) into the inner basket. Where are your hands? If the rods are uncharged,

the needle in the Charge Sensor will stay at zero. If the needle moves, then there is residual charge in the rods. To remove the residual charge, touch the charge producers to the outer basket of the grounded ice pail. Sometimes if residual charge is hard to remove, you can breathe on the rods. The moisture from your breath will remove the charges. It is difficult to remove all the charge since the rods are non- conducting. If you see a voltage change of less than one volt, that is good enough. Procedure A1: Charging by Rubbing Objects Together 1. Ground the ice pail, zero the Charge Sensor and make sure there is no charge on the charge producing rods (see step 7 under Setup A). 2. Hold one rod in each hand and lower them into the lower half of the inner basket, without letting them touch each other or the walls of the basket. Since there is no net charge in either rod, the needle in the monitor should not move and still read nearly zero. Press the Zero button on the Charge Sensor. Record the "initial" reading in row 1 of Table I. 1 2 3 4 Reading Initial After rub After separation Dark out Table I: Charge Sensor Voltages Run 1 Run 2 (V) (V) 0.003 0.004 -0.08 0.015 0.930 0.03 -0.110 1.200 Run 3 (V) 0.003 0.150 0.280 1.650 N.C 5 7 8 9 Both in Glass out Final Both out Sum 0.09 -0.800 -0.250 -0.003 0.01 0.3 0.810-1.346 019 0.19 01082 0.004 03 0.13 0.61 3. Do all of the following steps as rapidly as possible to minimize charge migration to the surroundings. 4. While inside the basket, briskly rub the two charge producer rods together and observe the needle in the monitor. Record the "after rubbing" reading in row 2 of Table I. 5. Stop rubbing. Still inside the basket, separate the rods and observe the needle in the monitor. Record the "after separation" reading in row 3 of Table I. 6. Take the dark rod out of the basket. Record the "dark out" reading in row 4 of Table I. 7. Insert the dark rod into the basket with the glass rod (not touching). Record the "both in" reading in row 5 of Table I. 8. Remove the glass rod. Record the "glass out" reading in row 6 of Table I. 9. Insert the glass rod into the basket with the dark rod. Record the "final" reading in row 7 of Table I. 10. Remove both rods. Record the "both out" reading in row 8 of Table I. 11. Rub the two rods together and then remove the charge from the glass one by touching it to the outside mesh cylinder. Ground the Ice Pail with your finger and zero the Charge Sensor. Repeat steps 2-10. 12. Rub the two rods together and then remove the charge from the black one. Ground the Ice Pail and zero the Charge Sensor. Repeat steps 2-10. Analysis A1 1. What can you immediately conclude about the charges on the glass rod and the dark rod based on the signs of the voltages in Run 1? glass is positive and dark is 2. Note that lines 3, 5, and 7 are exactly the same system so should have the same voltage. Any difference implies that there has been some charge lost or gained. In addition, line 8 should be zero unless some charge has transferred. Looking at these should allow you to estimate the uncertainties in the experiment and decide if numbers agree within the uncertainties. negative have 3. Recall that the voltage is directly proportional to the charge. Thus, if a voltage or 8 V implies 8 units of charge, a voltage of 12 V implies 12 units of charge. acquired opposite charge What do lines 1-3 imply? when we rub, the rods together, the rots should es to observer Tect a potential difference between the a significant upltag difference. The 5. Add line 4 to line 6 (don't forget the sign). Enter the sum on line 9. Charge rots. 6. Compare line 1 to line 9. What does this imply? The small increase in voltage of line 9 compared to line 1 is due to the unfinished dissipation of charge through the surroundin Procedure A2: Charging by Contact air on other materials. 1. Ground the ice pail and zero the Charge Sensor. Record the "zero" reading in line 1 of Table II. 2. Briskly rub the glass charge producer on a towel or napkin to charge it. 3. Insert the glass charge producer into the inner basket of the ice pail. Record the "initial" voltage on the Charge Sensor in line 2 of Table II. 4. Let the glass rod on the charge producer touch the wall of the basket. Record the "after touch" voltage on the Charge Sensor in line 3 of Table II. 5. Remove the glass rod. Record the "rod out" voltage on the Charge Sensor in line 4 of Table II. 6. Repeat steps 1-5 using the dark charging rod. Procedure A3: Charging by Induction 1. Ground the ice pail and zero the Charge Sensor. Record the "zero" reading in line 1 of the Charge by Table II. Glass Rod Induction (V) 0.016 3.400 -1.20 4.6 5,400 -1.18 0.02 2.600 -0.118 -2.68 2. Briskly rub the glass charge producer on a towel or napkin to charge it.. 1 Zero 2 3 State 4 Initial After touch Table II: Charge by Contact/Induction Glass Rod Dark Rod Rod out Contact (V) -0.07 Contact (V) 0.04 Dark Rod Induction (V) 701 14 -1 0.01 0.910 ion 1 esc A Z command DE DE JOUL W S Home 28 Word Fla et View. Insert Format Tools Table Window Help Atition B2-CO- sign Layout References Mailings Review View - AA Ax- A UX AA H Bert Phen C Fines te 3 H E F R $ V Procedure A2: Charging by Contact 1. Ground the ice pail and zero the Charge Sensor. Record the "zero" reading in line 1 of Table 11 Page 12 200 words Is English (United States F4 a 96 5 L B 6. Compare line 1 to line 9. What does this imply? The small increase in voltage of line 9 compared to line 1 is due to the unfinished dissipation of charge through the surrounding air or other materials. In theory in a perfect scenario, the voltage in line 1 should be the same as line 9. F5 E 32 21 6 uncertainties in the experiment and decide if numbers agree within the uncertainties. 3. Recall that the voltage is directly proportional to the charge. Thus, if a voltage or 8 V implies 8 units of charge, a voltage of 12 V implies 12 units of charge. N Zotero 4. What do lines 1-3 imply? When we rub the rods together, the rods should have acquired opposite charges to observe a significant voltage difference. The voltage would reflect a potential difference between the charge rods. Separating the rods should show a decrease in voltage due to dissipation of the charge through the surrounding air, leading to a reduction in the potential difference. 5. Add line 4 to line 6 (don't forget the sign). Enter the sum on line 9. C Fo 7 - C Electrostatic Charges Acrobat Tell me 4 M F7 Y 8 K Dil AURICHMG Emphasis FO < ( 9 command AARICHD O NOTAL L D F9 603 O A ARCDEs String ) O P 1 option <- Focus Styles Dictate Dane F10 ? 1 B F11 { 13 [ 11 +11 a Q-dark Sensitivity F12 33 N 09 Comments 12 Faive Mon 3:40 PM SP (10 Editing delete & Create PDF Request and share link Signatures 180% return Share shift 3. Without letting the rod touch the ice pail, insert the glass rod into the lower half of the inner basket. Record the "initial" voltage on the Charge Sensor in line 2 of Table II. 4. While the charge producer is inside the basket, momentarily ground the ice pail by bridging between the outer and the inner cylinder with your finger and then removing your finger. Record the "after touch" voltage on the Charge Sensor in line 3 of Table II. 5. Remove the rod from the ice pail. Record the "rod out" voltage on the Charge Sensor in line 4 of Table II. 6. Repeat steps 1-5 using the dark charge producer. Analysis A2/A3 1. What can you conclude from the data in the 2nd and 3rd columns (contact data) in the table? From row the touch you, the charges for all rods 2. Explain whats contact and after to what is happening when you induce a charge on the inner mesh cylinder. That is, explain the data in columns 3 & 4 of the table. Why does the sign change? only one of the columns had apsign change, I think there was human cror in the experiment. when you touch the inner mesh cylinder, you are allowing excess charge to flow to/from the ground. This influences the distributio of charge on the glass rod and the ice pail. The sign change between line 3 (after touch) and line 4 (rod out) is a result of manipulating the distribution of charge throus grounting and then observing the charge on the rot when it is removed./n Equipment 1 1 1 1 1 Charge Sensor Charge Producer rods and Proof Plane Faraday Ice Pail and Shield 4 mm Banana Plug Cord-Set of 5 Required but not included: 550 Universal Interface PASCO Capstone Electrostatic Charges Introduction PS-2132 ES-9057C ES-9042A SE-9750 UI-5001 The purpose of part A of this activity is to compare the results of three different methods of charging: (1) rubbing two objects together; (2) touching a charged object to a neutral one (charging by contact); and (3) grounding a neutral object while it is polarized (charging by induction). Part A will also demonstrate the law of conservation of charge. Theory A Electric Charges Electric charge is a fundamental property of nature. It comes in two types, called positive and negative. Positive charge is the type of charge carried by protons. Negative charge is the type of charge carried by electrons. As nearly as can be measured (better than 1 part in 10³⁰), the magnitude of the charge on an electron is the same as the magnitude of the charge on a proton. Atoms normally have the same number of protons and electrons, and this balance of charges makes them electrically neutral. Most objects are found in this neutral state. For an object to be positively charged, it must have more protons than electrons. For an object to be negatively charged, it must have more electrons than protons, disturbing the neutral charge balance. Forces between Charges Opposite charges always attract. Like charges tend to repel. At an elemental level, like charges always repel (electrons repel electrons, protons repel protons), but for macroscopic objects, non- symmetric charge distribution can result in an overall attraction between two objects that carry the same type of overall charge (positive or negative). Non-symmetrical charge distribution always results in an attraction between a charged object and an electrically neutral (overall) object. Charging: all charging processes involve the transfer of electrons from one object to another. For an object to become positively charged, it must lose some of its electrons. For an object to become negatively charged, it must acquire more electrons. 1. Charging by rubbing: When two initially neutral non-conducting objects are rubbed together, one of them will generally bind electrons more strongly than the other and take electrons from the other. The law of conservation of charge requires that the total amount of electrons be conserved. That is, electrons only move from one object to another, but no new electrons are created, nor do they disappear. Overall, the two objects when considered together still have zero net charge. 2. Charging by contact: When a charged object is touched to a neutral (or less charged) object, repulsive forces between the like charges result in some of the charge transferring to the less charged object so the like charges will be further apart. This effect is much larger for conducting objects. 3. Charging by induction: The protons and electrons inside any object respond to electric forces of attraction or repulsion. When an object is placed near a charged object, the charged object will exert opposite forces on the protons and the electrons inside the other object, forcing them to move apart from each other. One side of the object will become more positive than it was initially. The other side will become more negative, as electrons migrate internally. This condition is called polarization, a word that refers to the object having "poles," or opposite sides with different electrical states, even though the object as a whole may still be neutral. If a conductor is touched to the polarized object, some of the charge will transfer to the conductor. If the conductor is then removed, the object now carries a net charge different from its initial charge. For example, consider the sequence in Figure 1. Figure la shows an isolated neutral conductor. In Figure 1b, a negatively charged object has been placed near the neutral conductor, which is now polarized. Another conductor (elliptical) is shown but is not yet involved. In Figure 1c, the elliptical conductor touches the polarized conductor and some of negative charge transfers to the elliptical conductor due to repulsive from the negative charged object. In Figure 1d, the elliptical conductor is removed, taking some negative charge with it and leaving a net positive charge on the round conductor. In Figure le the negatively charged object has been removed. The charge on the round conductor re-distributes, but the overall charge on the conductor is now positive. Note that we have ignored polarization of the elliptical conductor. -+ -+-+-+ +-+-+- (a) +- ++-+-- \++-+-- (b) (c) +- +++- ++-+- (d) +- +++- ++-+- -+ + + + +-+-+ (e) Setup A 1. Connect the Charge Sensor to the Faraday Ice Pail as shown in Figure 2. Connect the alligator clip with the red band to the inner conductor and the ground (black alligator) to the outside conductor. The Charge Sensor is a device that can measure the voltage difference between small charges without affecting the charges. The "ice pail" is the inner conducting mesh cylinder and is called an ice pail for historical reasons. When a charge Q is placed inside the inner cylinder, the cylinder becomes polarized with a charge almost (exact if there wasn't an open top) equal to Q moving to the outside of the inner cylinder. The voltage between the inner and outer cylinders is directly proportional to charge on the outside of the inner conductor, so this gives a way to directly measure the change inside the “ice pail." www. 50 UNIVERSAL INTERFACE 2. Connect the Charge Sensor to one of the PASPORT ports on the 550. Create a Meter and a Digits display and select the voltage from the Charge Sensor on both. On the meter, click the auto-scale button. 3. Ground the Ice Pail touching a finger to both the inner and out cylinder at the same time. Then remove the finger from the inner cylinder and then the finger from the outer cylinder. The word "grounding" is used to mean removing all (really just most of) the excess charge. We generally do this by touching the system with a conductor that is much larger than the system, in this case our bodies. 4. Zero the Charge Sensor. This forces the Charge Sensor to read zero even if there is a charge on the Ice Pail. This is OK since we really are only interested in changes in the charge. 5. You may need to redo the grounding and/or zeroing of the Ice Pail during the experiment. It is very easy to transfer charge to the ice pail by touching it or even getting too close to it with a charged object. It may even acquire a charge sitting on the table for a while. To see how sensitive the system is, stick a finger down the axis of the inner cylinder (without touching the cylinder.) Now rub your fingers through your hair, or on your shirt, or shuffle your shoes on the floor and try sticking your finger back into the Ice Pail. See any difference? What happens if you touch the Ice Pail? What's the moral about where you put your hands during the experiment? Redo the grounding of the Ice Pail. 6. Click the Zero button again. 7. One at a time, insert the Charge Producer (one glass, one dark plastic, see image below) into the inner basket. Where are your hands? If the rods are uncharged, the needle in the Charge Sensor will stay at zero. If the needle moves, then there is residual charge in the rods. To remove the residual charge, touch the charge producers to the outer basket of the grounded ice pail. Sometimes if residual charge is hard to remove, you can breathe on the rods. The moisture from your breath will remove the charges. It is difficult to remove all the charge since the rods are non- conducting. If you see a voltage change of less than one volt, that is good enough. Procedure A1: Charging by Rubbing Objects Together 1. Ground the ice pail, zero the Charge Sensor and make sure there is no charge on the charge producing rods (see step 7 under Setup A). 2. Hold one rod in each hand and lower them into the lower half of the inner basket, without letting them touch each other or the walls of the basket. Since there is no net charge in either rod, the needle in the monitor should not move and still read nearly zero. Press the Zero button on the Charge Sensor. Record the “initial" reading in row 1 of Table I. 1 2 3 4 Reading Initial After rub After separation Dark out Table I: Charge Sensor Voltages Run 1 Run 2 (V) Run 3 (V) 5 6 7 8 9 Both in Glass out Final Both out Sum 3. Do all of the following steps as rapidly as possible to minimize charge migration to the surroundings. 4. While inside the basket, briskly rub the two charge producer rods together and observe the needle in the monitor. Record the “after rubbing” reading in row 2 of Table I. 5. Stop rubbing. Still inside the basket, separate the rods and observe the needle in the monitor. Record the "after separation" reading in row 3 of Table I. 6. Take the dark rod out of the basket. Record the “dark out” reading in row 4 of Table I. 7. Insert the dark rod into the basket with the glass rod (not touching). Record the "both in” reading in row 5 of Table I. 8. Remove the glass rod. Record the “glass out” reading in row 6 of Table I. 9. Insert the glass rod into the basket with the dark rod. Record the “final” reading in row 7 of Table I. 10. Remove both rods. Record the "both out" reading in row 8 of Table I. 11. Rub the two rods together and then remove the charge from the glass one by touching it to the outside mesh cylinder. Ground the Ice Pail with your finger and zero the Charge Sensor. Repeat steps 2-10. 12. Rub the two rods together and then remove the charge from the black one. Ground the Ice Pail and zero the Charge Sensor. Repeat steps 2-10. Analysis A1 1. What can you immediately conclude about the charges on the glass rod and the dark rod based on the signs of the voltages in Run 1? 2. Note that lines 3, 5, and 7 are exactly the same system so should have the same voltage. Any difference implies that there has been some charge lost or gained. In addition, line 8 should be zero unless some charge has transferred. Looking at these should allow you to estimate the uncertainties in the experiment and decide if numbers agree within the uncertainties.