Lorentz Compass 3.1 Free Download
Vilfredo Falls
Anchorage, AK 684 3.0 10.9 36.8 2.6 10.0 34.4 ... Following the analysis presented by Lorenz (2001), the two prism ... at 62 per cent RH.. ... points of the compass) was found to be preferable to the so-called Jeffersonian grid
A MEMS magnetic field sensor is a small-scale microelectromechanical systems (MEMS) device for detecting and measuring magnetic fields (Magnetometer). Many of these operate by detecting effects of the Lorentz force: a change in voltage or resonant frequency may be measured electronically, or a mechanical displacement may be measured optically. Compensation for temperature effects is necessary. Its use as a miniaturized compass may be one such simple example application.
There are many approaches for magnetic sensing, including Hall effect sensor, magneto-diode, magneto-transistor, AMR magnetometer, GMR magnetometer, magnetic tunnel junction magnetometer, magneto-optical sensor, Lorentz force based MEMS sensor, Electron Tunneling based MEMS sensor, MEMS compass, Nuclear precession magnetic field sensor, optically pumped magnetic field sensor, fluxgate magnetometer, search coil magnetic field sensor and SQUID magnetometer.
Gather the necessary materials and instruments, namely a DC current source, a plastic board mounted with several compass needles and a straight conducting wire passing through its center, and a permanent bar magnet.
Next, turn OFF the power supply and switch the positive and negative cables. Then, turn ON the power supply to reverse the direction of the current flowing through the wire and observe the compass needles again.
In the experiment with the compass needles, initially, the needles are randomly oriented. On application of the current, the compass needles align themselves with the local magnetic field in a circular pattern.
Centuries ago, the Song dynasty of China invented the first magnetic compass that was used for navigation. Since then we have relied on the compass, which works in tandem with the earth's own magnetic field, for direction.
The magnetic south pole of the earth is located near its geographic north pole. Thus, the magnetic north pole of a compass needle aligns to the earth's magnetic field and points towards the earth's geographic north.
You've just watched JoVE's introduction to magnetic fields. You should now know how to visualize magnetic fields using compass needles and understand how the Lorentz force of a magnetic field produced by a current affects another nearly parallel current. Thanks for watching!
Initially, I tried placing the magnet next to a compass so that the magnet's magnetic field is acting on the compass needle in a perpendicular direction to Earth's magnetic field. Then, using the angle the needle is displaced from pointing north (and earth's known magnetic field), the magnet's magnetic field can be worked out. Of course, however, the magnet's magnetic field is much stronger than that of the earth, so, the compass needle pointed directly at the magnet.
To solve this, I decided to back the magnet up far enough that the compass needle is displaced by a lesser amount. As I was not sure exactly how the distance between the magnet and the compass needle changes the magnetic field strength (perhaps someone can clear this up?), I took a number of measurements of the angle displacement at different distances.
Making a plot revealed that the magnet's magnetic field strength is inversely proportional to the cube of the distance from the compass needle. This concerned me because at distance 0 (the surface of the magnet), the magnetic field strength is "infinite." Of course, this is incorrect but I am not sure where I have gone wrong. Could someone point out the flaw in my understanding and suggest how the experiment could be modified to find the magnetic field strength on the surface of the magnet (or an alternate better experiment)?
Your magnet is essentially equivalent to a loop of wire with a given current (correct me if wrong). As such it would be expected that the Lorentz force will drop off $\propto \frac1r$. This is still likely imperfect, and I'm entirely unsure as to whether or not a compass could provide data without a laughably bad error.
You found correct correlations between deflection angle of compass and distance to your magnet. No error in your measurements. Monopole fields (such as gravity, electric charges, etc) drops in intensity with relation to distance as $\propto 1/r^2$. And dipole fields,- like electric charge $+-$ dipole or in this case - magnetic field (magnet with N-S poles),- drops in intensity by distance to field source like $\propto 1/r^3$. This is due to the fact that at the bigger distances- one pole cancels the effect of the other, so the net effect is that dipole field weakens faster due to superposition of these opposite poles.
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