Ward's World Activity Guides

+ ward ' s science Page 5 (We could use other liquids, like vinegar or lemon juice, but water is the easiest). The chemical reaction only occurs when the electrodes are connected by a conductor (the wire) and the circuit is closed. The electrons will flow through the electrolyte from the negatively charged anode (the zinc) to the positively charged cathode (the brass), and so create an electric current. The electrons always flow from the negative to the positive electrode. The battery will produce electricity as long as there is material for the chemical reaction to take place. As soon as you connect the clock to the electrodes and close the circuit, the zinc electrode starts to dissolve, losing electrons, while the hydrogen ions at the brass electrode gain electrons to form hydrogen gas. These reactions cause a current to flow through your circuit to the clock and back to the electrodes. The clock uses some of this energy and eventually the zinc rod will be eaten away. Station 9: Neodymium Magnets: Remember: you have 4 minutes maximum at each lab station. Turn the paper to 'red' when you arrive and flip it over to 'green' when you are done. READ This info about neodymium magnets and answer the questions on your answer sheet. FYI this info came with the big magnets we used with the dollar bill in one of the stations. Neodymium Magnets Warning: Rare earth magnets are extremely powerful, yet very brittle. Therefore, it is crucial to handle these magnets with extreme care to avoid injury and/or damage to the magnets. Fingers can be pinched between attracting magnets and magnets can chip if allowed to 'jump' at an attracting surface or object. These high-energy magnets can also easily damage any object or device, such as a computer or television that is sensitive to magnetic fields. Computer disks and video tapes should also be kept away. It is highly recommended that care and common sense be used whenever working with any type of magnet. How they are made: Rare earth magnets, such as neodymium magnets, are manufactured by first melting together the elements which make up the magnet. That material is then milled into a powder and dry pressed into shape in the presence of a magnetic field. Finally, the material is sintered (sintering is the process of compacting and forming a solid mass of material by heat or pressure without melting it to the point of liquefaction), aged, ground to dimension, magnetized and tested. They are called 'rare earth' magnets because the element neodymium is classified as a rare earth element in the Periodic Table. Applications/used for: magnetic separators, actuators, microphones, motors, automobile starters, computer hard disk drives, dot matrix printers, and speakers. Station 10: Moving Electrons: Remember: you have 4 minutes maximum at each lab station. Turn the paper to 'red' when you arrive and flip it over to 'green' when you are done. READ This and answer the questions on your answer sheet. You know that electricity is the movement of electrons. The ease with which electrons can move through a material is a conductor or an insulator. Resistivity is the measure of a material's resistance to the movement of electrons. It is measured in units of ohms x meters. Electrical insulators have a high resistance to the move- ment of electrons. Therefore, they have high resistivity values. Electrical conductors have low resistivity values. The table below lists resistivities for certain materials. Marvelous Magnets: An Exploration of Electromagnetism with Lab Stations (continued) Material Resistivity (ohms x m) Plastic 1,000,000,000,000,000,000 Rock salt 10,000,000,000 Sand 400,000 Graphite 0.00014 Aluminum 0.000000027 Silver 0.000000016

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