Download pdf - Measuring Magnetism

Method #1The most practical waypractical way of measuring the strength of a

magnet or any magnetic material is measuring the the amount of weight it can amount of weight it can

holdhold.

Procedures1. Clamp your magnet in a

clothespin. Tape the clothespin to the bottom of a cup as shown in the sketch.

http://sciencenetlinks.com/student-teacher-sheets/how-strong-your-magnet/

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.

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.

Method #2

To measure the magnetic field from a steady electric currentsteady electric current,

assume the value of the Earth’s magnetic fieldEarth’s magnetic field and the direction of the compass, then

solve for its flux density.

Procedures1. 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

component of about 2 x [10^-5] T.2 x [10^-5] T.

Values are computed using the current International

Geomagnetic Reference Field as

adopted by the International

Association of Geomagnetism and

Aeronomy. https://www.ngdc.noaa.gov/geomag/magfield.shtml

2. Put a current-carrying wire over the compass needle perpendicularly from the

north-pointing needleN

http://www.wired.com/2014/01/measure-magnetic-field/

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.


If you know for sure that the two magnetic fields are perpendicular, then based on the resulting right triangle you can say the following:


Method #3

For a more accurateaccurate computation, scientists use

specific instruments instruments or devicesdevices like gaussmeter

and magnetometer.

POCKET MAGNETOMETER

Magnetic fields can develop in many steel or iron objectssteel or iron objects if they have been exposed to magnetic fields, current, or magnetic fields, current, or

frictionfriction. This hand-held device detects residual magnetism in

steel parts quickly and accurately

http://www.lessemf.com/dcgauss.html

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.

http://www.lessemf.com/dcgauss.html

Superconducting Quantum Interference Device (SQUID)

• A very sensitive magnetometer used to measure extremely subtle extremely 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 in studies in biology. biology.

https://en.wikipedia.org/wiki/SQUID

Uses in Biology

MagnetoencephalographyMagnetoencephalography (MEG), for example, uses

measurements from an array of SQUIDs to make inferences inferences

about neural activity inside about neural activity inside brains. brains.

https://en.wikipedia.org/wiki/Magnetoencephalography

Uses in Biology

SQUIDs are being used as detectors to perform

magnetic resonance magnetic resonance imaging (MRI)imaging (MRI)The principle has been demonstrated by imaging human imaging human

extremitiesextremities, and its future application may

include tumor tumor screeningscreening..

https://en.wikipedia.org/wiki/Magnetic_resonance_imaging

Uses in of Earth SciencesThe use of SQUIDs in oil prospecting, oil prospecting,

mineral exploration, earthquake prediction mineral 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 of detection of gravitational waves.gravitational waves.

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.

How to measure Field Intensity using a Gaussmeter?

http://www.wikihow.com/Determine-the-Strength-of-Magnets

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.


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.


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 pole.


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.

