0:24 the Lorentz force: A magnetic field bends the current. 1:40 the question posted by Edwin Hall 4:00 It's not the voltage down the wire. It's the voltage across the wire. 4:34 the use of Hall Effect
Lots of people know lots of stuff about lots of things, but only a few have the gift of passing on that knowledge in a concise way that can be easily understood. Thanks much for the great explanation professor.
Having worked in a thermoelectric materials lab, the Hall effect is a very important metric to have! And now working on cars, Hall effect sensors are used all over the place, so this is a very useful video to help explain to customers why their speedometer isn't working or whatever! Thank you ❤
Another great thing about the Hall effect is that it was used to discover which particle actually moves in an electric current. In a wire, a flow of positive charges moving in one direction is indistinguishable from a flow of negative charges in the other. With the Hall effect, the charge buildup on the sides of the wire will be opposite depending on which charge is moving. This effect is the reason we know that electicity is due to electrons moving instead of protons.
these are used in sensors in many applications including most cars and machinery. They are called hall effect sensors. eg. crank angle sensor, proximity sensor, speed sensors, linear and rotary decoders
We use this for measuring RPM . Several small magnets are attached to shaft so that they pass by a Hall Effect sensor when the shaft is turning and we count the pulses generated by the sensor. There are other ways of measuring RPM, of course, but this method is cheap, reliable, and essentially frictionless.
Professor Bowley would be a greate teacher for basic (or advanced) electronics courses; it's really great how he can explain correct, significant and still in a way that is easy do understand.
You guys are great in that you make this sort of vital information simple for anyone's understanding. And just as importantly it seems you are doing something you enjoy thoroughly and comes naturally. Bravo and thank you.
@chrisofnottingham It's also used in brushless motors as a feedback mechanism so that the controller can switch on the right coil at the right place at the right time when a rotor magnet passes over it.
alarm door switches are normally just that, a switch (called a reed switch) hall effect sensors are used more in cars to detect the crank angle, or another fast moving magnet (as reed switches wont work fast or accurate enough, and reluctance type sensors are large and prone to noise)
Resistance is voltage over current not voltage times current. It's a mistake that I make sometimes too. I always enjoy the sixty symbols videos. Keep them coming.
Matter of fact, the Hall Effect is used in several modern automotive technologies such as the camshaft sensor, crankshaft sensor, and the Anti-Lock brake system.
It is also often used to measure rotational velocity or rotational position in various things. If there is something like the teeth on a cog or a shaft with a non uniform cross-section then a Hall effect sensor will give a varying reading as the thing rotates. This can be filtered and counted to give a speed or position. Advantages of this are that it is non contact method and also it continues to work in dirty environments when optical methods might be unsuitable.
You are correct todiwan. Conductive materials like metal have an interesting material property where electrons sort of just "float" around in the material and can thus be pushed around within the material (which is why they are conductive) The positive charge is the "absence" of all the electrons (it's positive relative to the more negative side).
@mcjhn The origin of the force on the current-carrying wire is the Lorenz force. Each moving electron that makes up the current experiences a Lorenz force, (the force that bends the path of the charge in the video) and the forces on each electron add up to give a net force on the wire which is proportional to the current times the strength of the magnetic field. The force is maximum when the wire lies perpendicular to the magnetic field. The Lorentz force is the common feature.
There’s been some developments on muon catalyze fusion using the hall effect And you can use to Hall effect control plasma to control the electron holes the positive and negative ions in the way the electrons line up with the positive negative ions and holes
A good every-day example for Hall effect sensors is in joysticks. The oldest joysticks were digital, meaning they basically pushed down a button when you moved the stick, kind of like on a modern controller's D-Pad. Then they started using analog potentiometers, which let current through based on how much of two metal surfaces are touching each other. Problem there is the metal wears out, gets dirty, or oxidizes. Now they're starting to use Hall sensors and permanent magnets; no degrading!
Sorry to disturb you and I don't know if someone has already said this but the drift velocity is the general velocity of the current. The actual velocities of the electrons are much higher although not all the the same direction at . Some are even going backwards. They also change. Drift velocity is the average of these velocities. Usually quite low. While there are photon transfers between electrons, the cause of a detected current is the actual movement of electrons.
@guitarfish83 A lot of great inventions use this effect. Measuring the rotation speed of a wheel, used for anti lock brake systems or frictionless speedometers on bicycles. The joysticks used in cranes or the analog controllers for video-games. Also it allows you to build instruments that measure the magnetic flux leakage which is handy for technicians to check the structural integrity of pipelines without having to dig them up or breaking walls. It's pretty useful. ;-)
@kristijan0kroflin Charge is a State, which is not dependend on other quantities, SI-Base System defines 7 units (see wikipedia for International System of Units, the one used in "Science" most of the time), one of which is Ampere (Electric Current, (which can be derived from moving Charges through a Surface (so C(Coulomb)/m^2(Square meters)). The thing is things depend on each other, so you can express it in different forms and they still mean the exact same thing, just in different quantities.
Burglar alarms use reed switches. Already been pointed out, I know. I like to be redundant. Atari made joysticks for their arcade games using Hall effect sensors (not all of them of course). "I, Robot", "Road Runner" and "Escape from the Planet of the Robot Monsters" all used Atari's Hall effect joystick.
@rahkshifan99 he's not bending light, he's bending a stream of electrons, which make a photofluorescent tube glow when they hit it, the light is no there when it's bend. (This is used in Old CRT Monitors, you got a stream of electrons and when they hit the screen making it glow in different colors, producing the image on the screen.)
this helped me understand my crankshaft position sensor for my vehicle......recent problem! thanks! i recently put in a NEW (but bad) CKP sensor and its apparently shorted internally- screwing up my fuel level gauge, ignition coil/ignitor(?) and setting off a host of other selonoids- et al! I cleaned all grounds, rebuilt my fuse box, new ECU, cleaned everything........no changes UNTIL i just now decided to swap back in the old CKP sensor. All the electrical clicking, etc went away immediately and Im not going thru the KEY RELEARN process for the new ECU
Great explanation. Thank God for the Internet. This professor has a passion for teaching - the not so good academics who seem to derive pleasure from making things seem 'harder' than they are... :-)
I remember a quote from Einstein saying, "If you cant explain it easily, you don't understand it well enough." This gentlemen is a giant. Enjoy your retirement sir, you have earned it.
In practical applications the Hall sensor is made out of a semiconductor where you can have electrons or holes or both. The reason is because you can manufacture it so that there are only few free charges available for the current transport, which means the few charges will have to move very fast in order to get the same current. And the faster the charges the stronger the Lorentz force and therefore the stronger the Hall effect. But I digress, let's go back to the plain metal conductor ...
@flux1969 No. That's a ferrite block which adds some parasitic inductance to the lead to prevent high frequency signals either from escaping from the monitor or getting into it from the outside and causing interference.
Most used for the ABS system of your car. Because you can sense with it if your tire is still rotating or its blocked. Together with an accelerometer you can see if the car is slipping over the road.
you can also set up a very easy burgler alarm you can actualy build yourself with a piece of iron. you put a magnet on the door and put an electrical contact with the piece of iron at the door that is held open by the magnetic field. if the magnet is moved away (due to the door opening) the metal snaps back and forms the electrical contact that you then can use to sound an alarm or something. no need for high tech expensive equipment if you can build it for 5€
@kristijan0kroflin electromagnetic phenomena are one of the best understood theories of science, the electromagnetic field theory as it's called. Magnetic Fields are produced by the movement of charged particles (Actually even a Magnet can be describes with the movement of the electrons in a metal, so called circular currents)
... in a metal you have free electrons and fixed atomic cores and in total the charges cancel each other out, so everything is neutral. If the Lorentz force now moves the electrons on one side the positively charged atomic cores remain on the other, because they can't move in the grid, hence the positive charge.
@mcjhn I loved the experiment as well. The idea came from the Feynman lectures and I used to do it in a lecture when there were demonstration benches in the lecture theatre. But videos with the word `work' in the title are not popular--- I'm beginning to understand why.
@ThatGuyFromAustria I would expect not, since not all metals are magnetic and those that are usually don't *produce* magnetic fields of any significant strength. I only have a high-school level of physics knowledge, though.
Here where I live the burglar sensors dont use this concept. They use a switch which is activated by a magnetic field. The magnetic field bend one of two metal wires that are very close together and make them touch.
If I remember correctly you can use hydrogen, which will give you a bluish colour, but I would imagine every noble gas would do the trick as well. However it will only work at a very low pressure! At atmospheric pressure the electrons won't even fly as far as a millimetre. Little note, the professor said the electrons were ionizing the gas, which isn't true for this particular tube. This tube is evacuated and the electrons are hitting the white scale where phosphorous produces the green light.
I thought it had something to do with the spin of the electron. spin up goes on one side while spin down goes to the other? I read an article about the recent discovery of the hall effect on light and they explained it by spin up/down electrons
I'm an electronic engineering student (1st year UG). I've used a PIC microcontroller with a Hall Effect sensor to measure the RPM of a rotating shaft (about a year ago). I think back then I would have benefitted from such an easy to understand explanation - it would have saved me from a lot of headaches! A very interesting video as per usual - the enthusiasm and friendliness of the professors’ is what makes this channel so great! Many thanks to Brady also. Thanks.
It isn't the same as a reed switch. Reed switch have a segment of broken wire that it reconnected when a magnetic force pulls both of them together, however I believed that reed switches were used in the door frame sensors. I suppose it depends on if you need a binary input or an analogue measurement.
@elimik31 Of course you are correct, and the glow comes from the fluorescence of the scale. My only excuse is that I am a stupid theoretician who is ignorant of such technical details. But I love the simple way the apparatus shows the effect of the Lorenz force.
iv been involved with alarms for 20 years nobody uses hall effect sensors yet. its all still argon filled reed switches. i think its because a reed switch only uses two cable cores so they are more cost effective and reliable
