This experiment will study the electromagnetic properties of an appliance and measure the internal current inside it using the magnetometer of your phone. The idea here is that steady currents will generate steady magnetic fields following the B.O. subart law. The magnetic field of a steady current carrying wire is just given as B is equal to mu not i over 2 pi r, where mu not is the permeability of free space, i is the current in the wire, and r is the distance from the wire to wherever the magnetic field is being measured. The figure here illustrates the application of the right hand rule to show where the magnetic field is oriented. In North America, the wall current runs on alternating current where the voltage oscillates up and down with a frequency of 60 hertz. This shows a typical graph of the voltage in an electrical line. The period of the wave here is 160th of a second. This shows the voltage on the vertical axis and time in the horizontal axis. This changing current will actually create a magnetic field around appliances that are drawing that current and that magnetic field will be changing also with 60 hertz. And to note in this measurement, we will not be able to measure a 60 hertz oscillation because of limitations in your phone sensors, but we will be seeing the change, specifically we'll be seeing the amplitude of the magnetic field changing. The objective of this lab is to detect the changes in a magnetic field when a household appliance is turned both on and off. We'll take the basic approach that we'll use the Firefox app on the phone to measure the magnetic field when the appliance is turned on. We'll estimate the distance between the magnetometer of the phone and the appliance, and we'll use that to calculate the approximate current in the appliance using the B of Svart law. For this lab, you will need to take a screenshot of the changing magnetic field and upload it to E-class and then answer a few short questions in an E-class lab questionnaire where you'll show your calculations and describe a bit about your setup. Let's take a look at how to collect data. To collect data in this lab, you will need a ruler or something to measure distance with. Your smartphone running the Firefox app and an electrical appliance. The kind of appliances that work best are things that do heating. For example, this is an electric kettle, a toaster oven works well, microwaves work well, as do hair dryers. You'll want something that draws a lot of current so we get a strong signal. The way we'll collect data is we'll take the Firefox app. We'll remove it from my phone, from the case because my case has a magnet in it and I'll collect some data. What I'll need to do is turn things around so that I zero out the magnetometer. Then I'll want to pause collecting data and place the phone next to the appliance. I'll start collecting data again now that the magnetometer has been calibrated. What I want to do is let it collect some data, turn on the appliance, notice the change in the magnetic field and then turn off the appliance. So we'll want a fold on and off cycle. Then we'll want to measure the distance from the center of the appliance to where your phone's magnetometer is. This is going to be an estimate because we have to measure to where we think the current is being drawn in the appliance. This can be a very rough number but it should be reasonable. Here I'm going to estimate around 10 centimeters and the answer of 1 millimeter or 10 meters would clearly be wrong but a few centimeters is probably correct. To collect data for this experiment we'll want to go into the Firefox app and again select the magnetometer data. The mode we want to use here is absolute. I've already calibrated my magnetometer and I've set it by the appliance. I'm just going to set it to taking data, noticing that the signal is a relatively constant 43 micro Tesla. I'm going to then turn the appliance on, off, on, off. Then I will pause collecting data. I'm going to then tap on the graph and zoom in. The thing that I want to measure in the data is the peak to peak amplitude of the signal. Here I'm going to estimate this bottom one using the pick data function at the bottom at about 42 micro Tesla. It's going to go up to about 43.6 micro Tesla. That's about 42.4 to 43.6. This gives us a peak to peak difference of 1.2 micro Tesla. We're going to use that information to calculate the magnitude of the current running through this appliance. Now that we've collected data, we want to go ahead and take a screenshot of the data, either by using the save menu in the upper right hand corner of the Firefox app or using your phone's screenshot capabilities. Go ahead and upload that screenshot to e-class showing where the appliance is turned on and off. We'll now estimate the current through the electric kettle. We start by looking at the peak to peak change in the magnetic field, which we measure to be 1.2 micro Tesla. This implies that the amplitude of the magnetic field is going to be 0.6 micro Tesla, and we estimated the distance between the magnetometer and the center of the appliance as 10 centimeters or 0.1 meters. We will now invert the BIOS of our law, as shown here, and substitute in the values from our experiment to determine the current inside the appliance. In this case, 0.3 amps. And that's it. You can go ahead, submit your screenshot and questionnaire answers, and you'll be finished with your first-year lab sequence in physics. Thanks for physicsing with us, and have a really great rest of your term. Bye-bye.