Measuring Magnetism

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  1. 1. Method #1 The most practical waypractical way of measuring the strength of a magnet or any magnetic material is measuring thethe amount of weight it canamount of weight it can
  2. 2. Procedures 1. Clamp your magnet in a clothespin. Tape the clothespin to the bottom of a cup as shown in the sketch.
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  4. 4. 2. Pull out one end of a paper clip to form a hook. Touch the hook to the magnet. 3. Carefully add paper clips to the hook, one by one.
  5. 5. 4. Weigh the total number of paper clips that you can hang onto the hook before the weight becomes too much for the magnet to hold and the paper clips fall.
  6. 6. Method #2 To measure the magnetic field from a steady electric currentsteady electric current, assume the value of the Earths magnetic fieldEarths magnetic field and the direction of the compass, then solve for its flux density.
  7. 7. Procedures 1. Assume the value of the Earth's magnetic field in your exact location. For example: The magnetic field is pointing directly NorthNorth with a horizontal
  8. 8. Values are computed using the current International Geomagnetic Reference Field as adopted by the International Association of Geomagnetism and Aeronomy.
  9. 9. 2. Put a current-carrying wire over the compass needle perpendicularly from the north-pointing needle N
  10. 10. magnetic-field/
  11. 11. 3. Now, when there is current in the wire, the compass needle will be deflected in the direction of the net magnetic field. Measure its angular displacement.
  12. 12. If you know for sure that the two magnetic fields are perpendicular, then based on the resulting right triangle you can say the following:
  13. 13. Method #3 For a more accurateaccurate computation, scientists use specific instrumentsinstruments or devicesdevices like gaussmeter and magnetometer.
  14. 14. POCKET MAGNETOMETER Magnetic fields can develop in many steel or iron objectssteel or iron objects if they have been exposed to magnetic fields, current, ormagnetic fields, current, or frictionfriction. This hand-held device detects residual magnetism in steel parts quickly and accurately
  15. 15. Simply place the test edge near or against the object being tested, and the needle gauge points to a reading representing the magnetism in the object at that site as well as polarity. Will also verify thoroughness of de-magnetizing.
  16. 16. Superconducting Quantum Interference Device (SQUID) A very sensitive magnetometer used to measure extremely subtleextremely subtle magnetic fields.magnetic fields. SQUIDs are sensitivesensitive enough to measure fields as low as 5 attotesla5 attotesla. This extreme sensitivity of SQUIDs makes them ideal for studies instudies in biology.biology.
  17. 17. wiki/SQUID
  18. 18. Uses in Biology MagnetoencephalographyMagnetoencephalography (MEG), for example, uses measurements from an array of SQUIDs to make inferencesinferences about neural activity insideabout neural activity inside brains.brains.
  19. 19. /Magnetoencephalography
  20. 20. Uses in Biology SQUIDs are being used as detectors to perform magnetic resonancemagnetic resonance imaging (MRI)imaging (MRI)The principle has been demonstrated by imaging humanimaging human extremitiesextremities, and its future application may include tumor ce_imaging
  21. 21. Uses in of Earth Sciences The use of SQUIDs in oil prospecting,oil prospecting, mineral exploration, earthquake predictionmineral exploration, earthquake prediction and geothermal energy surveyingand geothermal energy surveying is becoming more widespread as superconductor technology develops; they are also used as precision movement sensors in a variety of scientific applications, such as the detection ofdetection of gravitational waves.gravitational waves.
  22. 22. Gaussmeter Measures magnetic flux densitymagnetic flux density.. Excellent for measuring the flux density of air gaps in loudspeakers, motors etc. The probe is placed in the desired measuring location and the Gaussmeter measures the flux density at that point.
  23. 23. How to measure Field Intensity using a Gaussmeter?
  24. 24. 1. Calculate the baseline or original voltage by setting the maximum voltage to be read at 10 volts DC. 2. Read the voltage display with the meter away from a magnet. This is the baseline or original voltage, represented as V0.
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  26. 26. 3. Touch the meter's sensor to one of the magnet's poles. On some gaussmeters, this sensor, called a Hall sensor, built into an integrated circuit chip, so you actually touch the magnet's pole to a sensor.
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  28. 28. 4. Record the new voltage. Represented by V1, the voltage will either go up or down, depending on which pole of the magnet is touching the Hall sensor. If the voltage goes up, the sensor is touching the magnet's south-seeking pole. If the voltage goes down, the sensor is touching the magnet's north-seeking
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  30. 30. 5. Find the difference between the original and the new voltage. 6. Divide the result by the sensitivity value of the sensor. For example, if the sensor has a sensitivity of 5 millivolts per gauss, you would divide by 5. If it has a sensitivity of 10 millivolts per gauss, you would divide by 10. The value you receive is the field intensity of the magnet in gauss.
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