30 Jun, 2013
PRESENTATION: Charges are one of the basic properties of matter. If the positive and negative charges are balanced the object is said to be neuter and able to be charged, for example, if there is an electron transfer with another object.
- Can Like Charges Attract Each Other?, Nuri Balta, Phys. Teach. 50, 400 (2012)
- Static electricity and mylar, Harry Rheam, Phys. Teach. 28, 103 (1990)
INTRODUCTION: Static electricity is a phenomenon which we perceive every day. An accumulation of electric charges is produced in an object. This can produce an electrical discharge when this object is placed in contact with another. In 1832, Michael Faraday published the results of his experiments about current identity. Both the electricity induced from a magnet and the electricity produced by a battery, or the static electricity, are of the same nature.
OBJECTIVE: to test the behaviour of the static electricity and its influence over other bodies.
MATERIALS: Balloons, wool cloth, paper, water faucet.
SETUP: The two balloons for the experiment are prepared inflating and tying them.
- First case: The two balloons are rubbed one against the other and then we approach them while we see how the first influences the second by attracting it and making it move.
- Second case: We tear the sheet of paper in little pieces. We rub one of the balloons with the wool cloth and approach it to the papers checking how these are attracted by the balloon.
- Third case: we repeat the process to charge the balloon. We open the faucet and we approach the balloon to the flow and we observe how it changes its course due to the attraction that is produced.
EXPLANATION: The static current mainly appears due to the friction between two bodies. When there’s contact between two bodies (in our case the balloons) there are electrons of one of the bodies which pass to the other in such a way that one is left with less electrons (consequently more positive). As there is no way for the electrons to come back to the original body, this disbalance is kept and, as a consequence, the charged balloons attract each other and try to recuperate their initial net charge. In case the rubbing is discontinued the static electricity would disappear little by little. If the process of electric charge is kept, the disbalance will increase progressively up to a moment in which the discharge is produced as the electrons search the way back to their previous state, as it is the case during the electrical storms.
CONCEPTS: static electricity, electrical induction, electrostatics, polarization.
- Tipler P.A. Física, Reverté, 2010.
- De Juana J.M., Física General, Pearson, 2009.
- Serway R.A, Jewett J.W., Física, Thomson-Paraninfo, 2010.
- Martínez A.M., Morató, Rocamora, Sastre, Simón y Solsona, Introducción a la electrostática, Editorial Oikos-tau, 1995.
STUDENTS 2012-2013: Jacobo Creo, Julio Jurjo, Álvaro Rodríguez, Lorena Sampedro
LINK pdf STUDENTS (In Spanish):