Distance Dependence of Magnetic Field of a Bar Magnet
Module 8

The IOLab has a magnetometer as one of the available sensors, which measures the magnetic field in 3D. During the second week of our exploration of magnetic fields, you will use the IOLab to measure the strength of the magnetic field at several distances from a single magnet to quantitatively explore the relationship between B and r.

Objectives

In part 2 of the magnetic fields lab, you will:

Determine the background magnetic field produced by the Earth (and hopefully nothing else) and subtract out this background measurement to isolate the contributions of the total magnetic field due to a single neodymium magnet.
Calculate the magnitude of the total magnetic field from its x, y, and z components.
Compare quantitatively the magnetic field of a dipole as measured along its horizontal axis versus its vertical axis.

Read the Lab Document

Continue reading the lab instructions from last week. The lab instructions contains the theory you need to use to determine the magnetization of the dipole and make comparisons between measurement of the dipole's field along its axis versus perpendicular to it.

Download the Excel Workbook

Download the Excel workbook and add your measurements from the IOLab magnetometer to the data tables. Answer the comprehension questions providing justification with the data and analysis using linear regression (linear trendline analysis). Watch out for plotting the appropriate variable on the x and y axis of any plots.

Lab Set Up and Data Collection

Lab Materials and Setup Videos -

Lab Materials

IOLab
1 magnet
tape
metric tape measure/ruler
corkboard
blank 8.5 x 11 paper

Setup Videos

Calibrate and Testing the IOLab Magnetometer

Before taking data, make sure you calibrate the IOLab Magnetometer sensor. Open the IOLab program, with the IOLab device turned on and the Wifi dongle connected to your computer. Then, find the GEAR icon on the toolbar and select Calibration -> Accel - Magn - Gyro. Follow the instructions and make sure to click the SAVE button at the end to store the calibration as the default.

Next, test the IOLab magnetometer by placing the ioLab wheels up and collecting about three seconds of data. Hit Pause, then flip the device over 180 degrees so it rests on its wheels and record an additional three seconds of data. Each time the values for Bz should have a magnitude between 30 and 60 μT, depending on your latitude, as these values represent the vertical components of the Earth's magnetic field (assuming no other magnetic materials are nearby). The values will be on the low side if you live closer to the equator, and near the high side if you live closer to the poles.

Discussion Posting

In this week's discussion, post the results of the testing procedure described above. Next, post a screenshot of plots of d(cm) vs. B^-1/3, showing a trendline and the trendline equation for the measurements of the dipole's magnetic field when the dipole is moved with its axis is parallel to d (aligned along y-axis). Further, comment on the plots generated by other classmates:

Can you tell from the data which pole face of the magnet was closer to the sensor?
How linear is the relationship between d and B^-1/3. Is there evidence of any systematic errors in collecting data from the plots? What could be the sources of this error?
Why might someone have a legitimatly different value for magnetization of the dipole? Be specific.

Finally, what additional methodical considerations or details did you use to ensure that your data is representative of the field strength of the dipole (i.e. that our model described by equation 7 is valid)?

Upload and Submit

Submit your Excel workbook to the assignment Lab 8 - Distance Dependence on Magnetic Field Strength Excel Upload by Sunday at 11:59PM EST.

Distance Dependence of Magnetic Field of a Bar MagnetModule 8