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Running Head: PROBE DISTANCE AND VOLTAGE The Effect of the Distance between Metal Spheres on the Amount of Voltage Passed Between the Spheres Example 4 Liberty Union High School Friday, March 25 Mr. King 1 PROBE DISTANCE AND VOLTAGE 2 Abstract This experiment was conducted to look at the effect of the distance between two electrodes on the amount of voltage that passes between the electrodes. The primary materials required for this experiment are a gas tube transformer, a mutlimeter, two copper wire electrodes, a ruler, and a screwdriver. The hypothesis for this experiment is if a gap between two electrodes is made larger then less voltage is transferred between the two electrodes. The manipulated variable is the distance between the two electrodes. The responding variable is the amount of voltage passed between the two electrodes. The levels are the electrodes touching, the electrodes .3 centimeters apart, .6 centimeters apart, one centimeter apart, 1.2 centimeters apart, and 1.5 centimeters apart. There are four trials for each level. The constants are the number of trials, the transformer, a method used to find the voltage, and the location where the experiment was conducted. The control is the two electrodes touching. The results of the testing indicated that as the distance between the electrodes increased, the amount of voltage that passed between the electrodes increased. The mean voltage was zero when the electrodes were touching, 584 volts at .3 centimeters apart, 902 volts at .6 centimeters apart, 1,188 volts at one centimeter apart, 1,477 volts at 1.2 centimeters apart, and 9,065 volts at 1.5 centimeters apart. The experiment data did not support the hypotheses that if the electrodes are farther apart than the voltage would be lower. The results in this experiment were consistent with tests by Jochen Kronjaeger. PROBE DISTANCE AND VOLTAGE 3 Table of Contents Abstract……………………………………………………………………………………2 Introduction………………………………………………………………………………..4 History……………………………………………………………………………………..4 Significance………………………………………………………………………………..5 Facts……………………………………………………………………………………….6 Methods and Materials…………………………………………………………………….8 Results……………………………………………………………………………………..9 Conclusion……………………………………………………………………………….11 Tables…………………………………………………………………………………….13 References………………………………………………………………………………..14 PROBE DISTANCE AND VOLTAGE 4 Introduction Electricity has fascinated people for ages. From the invention of the light bulb to the luxury of the LCD television, we cannot imagine our lives without electricity. But what makes those things work? It is the simple science of the circuit and the power of voltage. Even the well-known insulator, air, has difficulty stopping the mighty voltage from pushing the current through a circuit. Under the right conditions, voltage, although decreased, can break through a gap of air. History There have been many scientists who have studied electricity. Two well-known physicists from Germany lead the way in the understanding of circuits and voltage. The first is Georg Ohm, who was a teacher at Jesuit College in Cologne (Georg Simon Ohm, 2000). The second is Gustav Kirchhoff who, in 1845, developed his circuit laws while he was a college student (Gustav Robert Kirchhoff, 2002). In 1827, Georg Ohm’s experiments determined that there is a relationship between voltage and resistance (Ohm's law, 2010). “Ohm’s law, in electricity, experimentally discovered relationship that the amount of steady current through a large number of materials is directly proportional to the potential differences, or voltage, across the materials” (Ohm's law, 2010). Ohm determined a mathematical formula for his law, which is that voltage equals resistance times current (Ohm’s law, 1996). The standard unit of measure of resistance was even named after him; it is called an ohm (Ohm's law, 1996). In 1845, Gustav Kirchhoff experimented with electrical circuits and developed two theories that are called Kirchhoff’s laws (Kirchhoff’s circuit laws, 2009). His first PROBE DISTANCE AND VOLTAGE 5 circuit law, also known as Kirchhoff’s current law, states that “the amount of current flowing towards a point should be equal to the amount of current flowing away from that point” (Kirchhoff’s circuit laws, 2009). Kirchhoff’s second circuit law, also known as Kirchhoff’s voltage law, states that “the sum potential difference (drop or gain) in a closed circuit is zero” (Kirchhoff’s circuit laws, 2009). These two scientists developed their theories in the 1800s. Since then, there have been many scientists who have experimented with electricity. Many more have invented valuable electrical tools. Despite the new knowledge in electricity, the theories of Georg Ohm and Gustav Kirchhoff have not changed and are still used today (Ohm's law, 2010; Kirchhoff’s circuit laws, 2009). Significance Electricity affects just about every part of a human’s life in today’s modern times. Electricity provides power to many of the tools most people uses throughout the day. From the alarm clock that wakes a person in the morning to the television a person watches at night, electricity makes it all possible. Conducting experiments with electricity helps people to understand how electricity works. Experiments can deepen knowledge about how circuits function, how voltage is measured, and how voltage can vary in a circuit. Studying electricity is valuable to everyone, especially to one who wants to be an engineer. The hypothesis for this specific experiment is that if a gap between two metal spheres was made larger less voltage is transferred between the two spheres. PROBE DISTANCE AND VOLTAGE 6 Facts All substances are made up of atoms (Riley, 1998). Small particles, called protons, neutrons, and electrons, are in the atom. The electron, which has a negative charge, spins around the proton, which has a positive charge, and the neutron, which has no charge. Most atoms have a balance of protons and electrons; this means the atom is neutral. Sometimes an object becomes charged and the atom is not balanced. A charged object tries to attract other charged particles so it can become balanced again. These charged particles cause electricity (Woodford, 2010). Electricity is energy that has two different forms, current electricity and static electricity. “Current electricity is caused by the movement of charged particles.” In static electricity, there is no movement of the charge (Woodford, 2010). Current electricity flows in a circuit. Circuits are in every electrical device. A simple circuit has an electrical source, wires, a switch and a bulb. A closed circuit allows electricity to flow around the circuit; an open circuit does no allow electricity to flow. Voltage is the energy that makes the electricity flow in the circuit and is measured in volts (Riley, 1998). Air is an insulator; another word for insulator is dielectric. This generally means that voltage cannot travel across an air gap. However, when dielectric breakdown occurs, voltage can travel through the air gap. This is because “when the voltage becomes sufficiently high in an air gap, electrons are stripped from the air molecules, ionizing the air and allowing current to flow.” Lightning is an example of dielectric breakdown (How far can sparks jump, 2002). The voltage in the circuit is now called dielectric breakdown voltage (Science Buddies, 2002). PROBE DISTANCE AND VOLTAGE 7 The understanding of electricity requires the knowledge of several key terms. A circuit is “a path along which a current of electricity can be made to pass” (Woodford, 1998, p. 30). This experiment will require a circuit. “Current is the flow of electricity in a circuit” (Woodford, 1998, p. 30). A current will flow through the circuit in this experiment. Voltage is “the energy that makes the electricity flow in the circuit and is measured in volts” (Riley, 1998). Voltage will be measured during the experiment. A voltmeter is an instrument that measures voltage. A voltmeter will be used to measure voltage in this experiment. Some additional terms that are important are piezoelectricity, piezoelectric crystals, dielectric, and dielectric breakdown. “Piezoelectricity is the ability of certain crystals to produce a voltage when subjected to mechanical stress” (Piezoelectricity – definition, 2010). A piezoelectric barbecue fire starter will be used in this experiment. Piezoelectric crystals are a small-scale energy source (Piezoelectric Crystals, 2006). The crystals in the fire starter will be the energy source. A dielectric is an insulator. Air will be the dielectric in this experiment. “When the voltage becomes sufficiently high in an air gap, electrons are stripped from the air molecules, ionizing the air and allowing current to flow” (How far can sparks jump, 2002); this is dielectric breakdown. Dielectric breakdown is expected to occur between the two metal spheres. PROBE DISTANCE AND VOLTAGE 8 Methods and Materials The approach to understanding electricity and performing an experiment to measure voltage will require research on the topics of circuits, voltage, and how electricity passes between objects. Like most electrical research, this experiment will use a circuit and measure voltage using a voltmeter. The research will require knowledge of piezoelectricity because the experiment will use a piezoelectric barbecue fire starter as the energy source. This differs from most circuit experiments that typically use a battery as the energy source. In addition, the circuit will have an “air gap” between the two metal spheres to create dielectric breakdown. This also differs from most circuit experiments that have wires that connect the circuit, meaning that there are no gaps in the circuit. The materials required for this experiment are: a barbecue fire starter, a voltmeter, two metal spheres, modeling clay, electric tape, stiff cardboard, a ruler, and a screwdriver. The hypothesis for this experiment is that if a gap between two metal spheres is made larger, then less voltage is transferred between the two spheres. The manipulated variable is the distance between the two metal spheres. The responding variable is the amount of voltage passed between the two spheres. The levels will be the metal spheres touching, .3 centimeters apart, .6 centimeters apart, 1 centimeter apart, 1.2 centimeters apart, and 1.5 centimeters apart. There will be four trials for each level. The constants will be the number of trials, the starter, method used to find the voltage, and the location where the experiment is conducted. Finally, the control will be the two metal spheres touching. PROBE DISTANCE AND VOLTAGE 9 Results The effect of the distance between two electrodes on the amount of voltage passed between the electrodes is summarized in Table 1.1 and Table 1.2. During testing, there was a need to change the instrument used to measure the voltage. The original plan was to use a voltmeter; however, the voltage in the experiment was too high and the voltmeter was damaged. Therefore, an oscilloscope, an instrument used to measure high voltage, was used to try to measure the voltage. During the testing with the oscilloscope, the metal spheres were removed because a consistent connection could not be established. Two copper wire electrodes were used. In addition, when using the oscilloscope, the voltage readings were inconsistent and difficult to capture. This was due to the fluctuating charge from the piezoelectric fire starter. Therefore, the energy source was changed to a gas tube transformer. Because the gas tube transformer is high voltage, a high voltage probe and an electronic multimeter was used to measure the voltage. The first test was measuring the voltage with the electrodes touching. The voltage measurement with the electrodes touching was zero in all four trials. The voltage is zero because the touching electrodes formed a closed circuit (a complete circuit). No dielectric breakdown occurred. The range and the mean with the electrodes touching is zero. The second test was with the electrodes .3 centimeters apart. The measured voltage was: 616 volts on trial one, 440 volts on trial two, 684 volts on trial three, and 596 volts on trial four. The range was 244 volts, and the mean was 584 volts. These results indicate that dielectric breakdown was occurring. A low amount of voltage was PROBE DISTANCE AND VOLTAGE 10 needed to create dielectric breakdown when the electrodes were .3 centimeters apart. After this test, there is evidence that the hypothesis may be incorrect. The third test was with the electrodes .6 centimeters apart. The measured voltage was: 710 volts on trial one, 872 volts on trial two, 1,006 volts on trial three, and 1,020 volts on trial four. The range increased only a little from the first test to 310 volts. The mean was 902 volts. More voltage was needed to create dielectric breakdown between the two electrodes. Results from the third test indicate that the hypothesis is incorrect. More voltage passed between the electrodes as the distance between the electrodes increased. The fourth test was with the electrodes 1 centimeter apart. On this test, over 1,000 volts were needed to create dielectric breakdown. The measured voltage was: 1,080 volts on trial one, 1,044 volts on trial two, 1,272 volts on trial three, and 1,356 volts on trial four. The range increased only by a few volts from the third test, increasing to 312 volts. The mean was 1188 volts. These results continue to indicate that more voltage is needed to create dielectric breakdown as the electrodes are moved apart. These results continue to prove that the hypothesis is incorrect. The fifth test was with the electrodes 1.2 centimeters apart. The voltage measurements on this test were very close to the voltage measurements on the onecentimeter test. The measured voltage was: 1,414 volts on trial one, 1,460 volts on trial two, 1,472 volts on trial three, and 1,560 volts on trial four. The range was 146 volts, indicating that the results were close the four trials. The mean was 1,477 volts. Again, these results indicate that more voltage is needed to create dielectric breakdown as the PROBE DISTANCE AND VOLTAGE 11 distance between the electrodes increase and that the hypothesis for this experiment is incorrect. The sixth and final test was with the electrodes 1.5 centimeters apart. On this test there was no spark created between the two electrodes because there was not enough voltage for dielectric breakdown to occur. However, there was still a flow of electricity between the two electrodes. The measured voltage was: 9,240 volts on trial one, 8,540 volts on trial two, and 9,240 volts on trials three and four. At this distance, the range was the biggest with a difference of 700 volts. The mean was also the highest; the mean was 9,065 volts. Even though there was no spark, this test still indicates that there is a large amount of voltage passing between the two electrodes. Conclusion The purpose of this experiment was to determine the effect of the distance between two electrodes on the amount of voltage that passes between the electrodes. As the distance between the electrodes increased, the amount of voltage that passed between the electrodes increased. The mean voltage when the electrodes were 1.5 centimeters apart (9,065 volts) was greater than the voltage when the electrode were touching (zero volts). The data does not support the hypotheses that if the electrodes are farther apart the voltage would be better. The results in this experiment are consistent with tests by Jochen Kronjaeger. Kronjaeger found that voltage of 5,000 volts was needed for a distance of .42 centimeters, 10,000 volts for a distance of .85, centimeters, and 15,000 volts for a distance of 1.3 centimeters (Kronjaeger, 2000). While Kronjaeger’s results indicate that the amount of voltage that passed between the electrodes increased as the distance between the electrodes increased, his results show a higher level of voltage at PROBE DISTANCE AND VOLTAGE 12 each distance. This discrepancy could result from different atmospheric conditions. Kronjaeger’s testing was in dry air (Kronjaeger, 2000). This experiment was conducted in a normal household setting, which means there was humidity. Kronjaeger also used needles as the electrodes (Kronjaeger, 2000). This experiment used copper wire as the electrodes. Additional studies could be conducted to determine the amount of voltage transferred between needles using a more powerful energy source with the experiment being conducted in dry air. PROBE DISTANCE AND VOLTAGE 13 Appendix A Table 1.1. The effect of the distance between two electrodes on the amount of voltage (V) passed between the electrodes. Distance Between the Electrodes Touching .3 cm .6 cm 1 cm Trial 1 Trial 2 Trial 3 Trial 4 0 616 V 710 V 1,080 V 0 440 V 872 V 1,044 V 0 684 V 1,006 V 1,272 V 0 596 V 1,020 V 1,356 V 0 244 V 310 V 312 V 0 584 V 902 V 1,188 V 1.2 cm 1.5 cm 1,414 V 9,240 V 1,460 V 8,540 V 1,472 V 9,240 V 1,560 V 9,240 V 146 V 700 V 1,477 V 9,065 V Range Mean PROBE DISTANCE AND VOLTAGE 14 Appendix B Table 1.2. Graph of the data in Table 1.1. As the distance between the electrodes increased, the voltage passed between the electrodes increased. 9,000 8,000 Voltage (V) 7,000 6,000 Trial 1 5,000 Trial 2 4,000 Trial 3 Trial 4 3,000 2,000 1,000 0 0 0.3 0.6 1 1.2 Distance Between the Electrodes (cm) 1.5 PROBE DISTANCE AND VOLTAGE 15 References Georg Simon Ohm. (2000). Retrieved from School of Mathematics and Statistics, University of St Andrews, Scotland website: http://www-groups.dcs.st-and.ac.uk/~history/Biographies/Ohm.html Gustav Robert Kirchhoff. (2002). Retrieved from School of Mathematics and Statistics, University of St Andrews, Scotland website: http://www-history.mcs.st-and.ac.uk/Biographies/Kirchhoff.html How far can sparks jump? (2002). Retrieved from Science Buddies website: http://www.sciencebuddies.org/science-fair-projects/project_ideas/ Elec_p032.shtml Kirchhoff's circuit laws. (2009). Retrieved from Connexion website: http://cnx.org/content/m30943/latest/ Kronjaeger, J. (2000). Jochen's High Voltage Page. Retrieved from http://www.kronjaeger.com/hv/hv/msr/spk/index.html Ohm's law. (1996). Retrieved from NASA website: http://www.grc.nasa.gov/WWW/k12/ Sample_Projects/Ohms_Law/ohmslaw.html Ohm's law. (2010). Retrieved from Britannica website: http://www.britannica.com/ EBchecked/topic/426070/Ohms-law Piezoelectric Crystals. (2006). Retrieved from Renewable Information website: http://www.greenenergyhelpfiles.com/piezoelectricrystals.htm Piezoelectricity - definition. (2010). Retrieved from word IQ website: http://www.wordiq.com/definition/Piezoelectricity Riley, P. (1998). Electricity. Connecticut: Grolier Publishing Co., Inc. PROBE DISTANCE AND VOLTAGE 16 Woodford, C. (2010). Experiments with Electricity and Magnetism. New York: Gareth Stevens Publishing.