Science Fair

We were trying to measure magnetism with distance. Our research question was “What is the effect of distance on Magnetic Field / Magnetism?”

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We believed this was an important topic to investigate not necessarily due to it’s relevance in day to day life, but because we believe that it is an interesting topic that covers multiple fields in our investigation. Overall it is important because magnetism is all around us, yet we can’t measure this without a special setup. I find the idea of magnetism and magnetic fields rather interesting.

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We have set up the proper setup attempting to use two different hall effect sensors. Sadly we couldn’t get our hands on the proper component due to covid-19. We have all if the bits and pieces assembled though. The circuit seemed to be efficiently powered. We didn’t have a proper magnet to test on the circuit. So, it is ‘possible’ the circuit may work.
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We planned on purchasing the proper Hall Effect Sensor and a proper magnet.
What follows is our current procedure and parts list:

Parts:

  • Breadboard
  • 9 V battery
  • 9 V battery snap connector
  • LM7805 voltage regulator
  • A1302 Hall effect sensor
  • Jumper wires (assorted)
  • Multimeter
  • Magnets (2)
  • Wire stripper and cutter*
  • Soldering Iron**useful but not mandatory.

Procedure:

*Set up the experiment area using the materials stated previously to build the gaussmeter circuit,

Make sure that the multimeter displays 2.50 Volts when no magnets are nearby, move the magnet towards the hall effect sensor to test magnetic field (when a magnet is brought nearby the voltage should fluctuate, if the mutimeter shoots up to 5 volts use a smaller magnet,

Prepare a data table to record distance and voltage,

make sure the sensor is not near any magnets. Record the voltage displayed on the multimeter in your lab notebook and label it as “V0“.

Now, starting with the magnet touching the face of the sensor (a distance of zero), record the voltage displayed on the multimeter.

Slide the magnet directly away from the sensor (make sure you move it straight backwards, not to the side). Record the new distance and voltage in your data table.

Repeat step 6 until the voltage stops changing.

Repeat steps 5–7 at least two more times, for a total of at least three trials.

Calculate an average voltage for each distance.

Now, convert voltage to magnetic field strength. You can do this using information from the sensor’s datasheet, which says that the sensor has a sensitivity of 1.3 mV/G (note that the sensitivity is given in millivolts (mV) and you took your readings in volts (V), so you will need to convert from V to mV). You can convert voltage to field strength using the following equation:

Equation 1:

B=V0−V1.3

  • B is the magnetic field strength in gauss (G).
  • V0 is the voltage when there is no magnet nearby in millivolts (mV).
  • V is the voltage recorded at a certain distance in millivolts (mV).
  • 1.3 is the sensor’s sensitivity in millivolts per gauss (mV/G).

Make a graph of magnetic field strength versus distance.

*Breadboard Setup:

Voltage regulator

E2, E3, E4
Writing facing to the left

Hall effect sensor

B9, B10, B11
Writing (smaller side) facing to the left. Look carefully, the writing is hard to see!

Jumper wires

C2 to (+) bus
B3 to (+) bus
C4 to C9
A10 to (-) bus
(-) bus to multimeter
A11 to multimeter

9 V battery and snap connector

Red lead to (+) bus
Black lead to (-) bus

Multimeter

Set to measure 20 volts DC.

Black probe in COM. Connect to ground bus with alligator clip and jumper wire.

Red probe in VΩmA. Connect to A11 with alligator clip and jumper wire.

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Me and Tom talked to Ms. Casey and I talked to a guy at an electronics store for a couple minutes.


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