• ### 02/10/2019: Making the Mag Field with Permanent Magnets

To generate a steady B-field for our experiment, we have two options to choose from:

1. Permanent Magnets
2. Electromagnets

Before I choose a path, I'd like to do a quick study to determine the cost of building a magnet with a 1 Tesla flux density through a 1" x 1" area.  If more than 1 Tesla is needed, we can approximate the cost as a linear function of flux density.

Using Permanent Magnets:

Benefits of using permanent magnets are:

1. Different sizes, shapes, and strengths readily available
2. Stacking smaller magnets is equivalent to a single magnet of the same thickness
1. Flux density (B) dependent on the magnet's dimension in the direction of the magnetic field's axis
3. Setup would require a simple mounting fixture

Some cons:

1. If using multiple small magnets, the B-field will not be uniform in certain places (compared to a larger permanent magnet or electromagnet) due to the gaps between the magnets.  (Not a show stopper)
2. Can get expensive as the number of magnets needed is increased to increase the B-field.

Example Jig set up:

• Using the B884-N52 rectangular magnets stacked in two rows, we can get a B-Field of ~ 1 Tesla (0.99 Tesla)
• Total cost would be ~\$30.  The jig would be made from scrap wood I have laying around.

Analysis using an electromagnet coming in the next log...

• ### 01/21/2019: Hall Voltage Calculator

Added the Hall voltage calculator.  Right now I only have copper in there, but feel free to use.  The process will be the same for different materials, just plug in the correct values.

• ### 01/21/2019: Deviating from the Original Experiment

There are going to be some differences between my experiment and the original:

1. use copper, or some other metal clad board/insulator (price is king) for the hall element, not gold leaf
2. use copper wires, not brass because why brass when there is plenty of copper wire in my lab stock?
3. wires will be soldered directly to the element which should provide less terminal resistance than using highly polished brass contacts
4. use an electro-magnet to generate the B-field with a split-core to place the hall element where the magnet shall have: a) a high permeability core, and b) a small split in the core as thick as the hall element +/- 2mm to minimize reluctance (and loss of flux) in the magnetic
5. use a better power source, Brunsen cells are somewhat out-of-date
6. to measure the hall voltage, I'll potentially need a high-precision amplifier and a current sense resistor to make my own galvanometer.

For the Hall element, I'd like to use either 1 oz or 0.5 oz copper clad board since minimizing thickness is key.  In Hall's paper, he stated that even using a strip of copper that 9cm x 2cm x 250um (that's micrometers, 10-6  meters) would fail to yield a detectable transverse voltage.  However, this could have been due to the limitations of the equipment he was using at the time.

I'll  have to do some more research as to the reason for this, but it may still be worth a shot to try the 1oz or 0.5oz copper since their thickness is significantly less than 250um, 30um down to ~17um respective to the copper clad weight.