• This lab usually runs before students see Faraday's law in lecture. TA's must be prepared to provide a conceptual overview. Give the students the theory and tell them that the differential and integral forms can be used as the basis for two different measurements of the ambient field in the lab. Emphasis is on letting students figure out how to use the device to accomplish the measurement.
• The induced current in the wire loop that wraps around the IoLab body is very small, even using the hi gain amp input on the device. For 2026 I wound some 10 turn coils that ended up being a tight on the IoLab bodies.
• I used to have the students swap coils with a stand alone loop of wire to look at the induced current from a pair of Heath Coils driven by a function generator. I cut this in 2026 because it was not well integrated with the measurement of the ambient field, and also because students were breaking off the wires in the input sockets which are difficult to dig out. I recommend leaving the IoLab devices which currently have the 10 turn wires installed, dedicated to this lab. There are more than enough IoLabs for this.
• I based this lab on work done by the creator of the IoLab, Matt Selens at UIC. I down loaded his description of the two methods for measuring the ambient field, they are very well done.
  • Integral Method
  • Differential Method

Setup is dirt simple. A single IoLab device with the 10 turn coil wrapped around its body.

Additionally each computer running the IoLab device needs the following file in order to read out enough digits for the induced emf.

This file needs to be present in the root directory of the IoLab software to increase the number of significant figures in the display of the recorded magnetic fields.

file name = config.json

"earthMagneticFieldZ": -48.55,
"sensors": [
  {
    "code": 12,
    "desc": "High Gain",
    "shortDesc": "HG",
    "label": "G+ - G-",
    "unit": "mV",
    "legends": ["Voltage"],
    "numberOfDigits": { "mean": 5, "sigma": 5, "area":5 },
    "scales": [-1, 1],
    "autoScaleY": false
  }
]

Since students typically do this lab before seeing the material in lecture, I think it could be expanded into 2 days. Day 1 would be an introduction to induced currents. Students could map out the parameters of Faradays law using a loop of wire in the high gain input of the IoLab with magnets oscillating on springs, a function generator connected to a pair of heath coils, etc. Then day 2 would be using Faradays law to measure the ambient field. Day 1 would replace e/m.