Mrs. Blevins' Science - Home



General questions *The following webpage (and the pages that follow by hitting the “next” button) contain good information about the source and properties of magnetism. Use this site to answer questions 1-5 below. 1) What causes magnetism inside the atom? The electrons that are in constant motion around the nucleus of an atom. Electrons carry a negative electrical charge and produce a magnetic field as they move through space. A magnetic field is produced whenever an electrical charge is in motion2) Why are unpaired electrons more significant than paired electrons in terms of magnetic properties? Electrons in a pair spin in opposite directions. When electrons are paired together, their opposite spins cause their magnetic fields to cancel each other so no magnetic field exists. Materials with some unpaired electrons will have a magnetic field.3) What causes a material to be classified as “ferromagnetic”? Name some examples of ferromagnetic materials. Ferromagnetic?materials are very attracted other magnetic fields. They have a strong attraction to magnetic fields and are able to retain their magnetic properties after the other magnetic field has been removed.Iron, nickel, and cobalt are examples of ferromagnetic materials.4) What is a magnetic domain? Sketch two images of a material that has magnetic domains, one that is magnetized and one that is unmagnetized. A magnetic domain is a small region within ferromagnetic materials. Ferromagnetic materials become magnetized when the magnetic domains within the material are aligned. UnmagnetizedMagnetized5) Sketch a bar magnet. Label the poles of the magnet with an “N” and an “S”. Draw magnetic field lines (with direction).Magnetism and Plate Tectonics *Read through the following website and answer the questions below. 1) What is basalt and how do scientists use it to determine the direction of Earth’s magnetic field over time? After molten lava emerges from a volcano, it solidifies to a rock known as basalt, which is slightly magnetic. When it cools its magnetization is in the direction of the local magnetic field at the time. If a volcano has produced many lava flows scientists can analyze the magnetizations of the various flows and from them get an idea of how the direction of the magnetic field has changed.2) How does geomagnetism help scientists understand the motion of Earth’s plates?As the "plates" on each side of ridges in the seafloor are pulled away, lava comes up from the middle, hardens and "records" the current magnetic field. The sea-floor is like a giant tape recorder with twin tapes recording the Earth's magnetism at the time they emerge from the mid-ocean ridges and then travel in opposite directions. **You do not have to draw this image**Field Reversals *Read this 2-page article about geomagnetism from National Geographic 1) How long have scientists been recording the strength of the Earth’s magnetic field? Since 1845.2) What is happening to the Earth’s field right now? Earth's magnetic field is fading. If it continues to fade, the field may collapse altogether and then reverse. Compasses would point south instead of north.3) How does the magnetic field act like a shield? The magnetic field shields most of our planet from charged particles that come from the sun. The field deflects the speeding particles toward Earth's Poles. Without our planet's magnetic field, Earth would be subjected to more cosmic radiation.4) What animals use the Earth’s magnetic field for navigation? Birds, turtles, and bees.5) What is the average time between field reversals? On average, about once every 200,000 years.6) When is the last time the Earth’s field reversed? The last time Earth's magnetic field flipped was about 780,000 years ago.Magnetic Declination *Answer the next several questions using the following webpage as well the link that reads, “What is Magnetic Declination?” 1) What is magnetic declination and what causes it? The direction in which the compass needle points is known as magnetic north, and the angle between magnetic north and the true north direction is called?magnetic declination. 2) What do the terms “geographic north” and “magnetic north” mean? Magnetic North is the North of earth’s magnetic field whereas geographic North is the true North.3) What is the magnetic declination in Chicago (include + or - )? (To find this enter Chicago, Illinois in the location on the left side of the screen)Magnetic declination: -4° 2'?Declination is?NEGATIVE (WEST)4) If you wanted to walk in the direction of true north in Chicago, would you want to walk to the left or right of where a compass needle points? Right5) Pick another city and find it’s magnetic declination.City: ______________________State: _____________________Magnetic Declination: _____________________If you were in this city, would you walk to the left or right of were the compass needle points, if you wanted to walk in the direction of true north? ................
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