Induced current in a wire | Physics | Khan Academy
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- Опубликовано: 5 сен 2024
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Sal determines the current and EMF induced in a wire pulled through a magnetic field. Created by Sal Khan.
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Did anyone else think that the most impressive part about this video was how good he drew that hand?
this guy creates insanely cool hands
yeah with four fingers
@@alend98 5:52 there's 1 finger pointing towards the screen
This guy teaches better than all my teachers. He takes 1/6th the time they do to explain it, and it still feels like he's going slow. And it only feels slow because it's so clearly and perfectlyexplained.
Never seen "how is electricity generated" explained through applying the mathematical equation, always been told it is "cutting the field lines".
Very useful. I will be saving a link to this video.
Wow, thank you so much for the magnetism explanations!!! I've been beating my head looking at my book and trying to figure it out. You explained it very well. I like the RH rule you give. It makes so much more sense than the one my prof gave us.
I really respect this person. Really
doing a good deed..!
SO COOL!! One of the most interesting things I've learned. Thank you!
I too learned the left hand rule. It's perfectly ok, just a different way of learning/remembering it! Just try to picture doing it your way whenever he uses his method.
You can use the solenoid convention right hand rule....after you figure out the fact that as the wire is move to the left or to the right, the side of the wire facing the dots (magnetic field out of the page)...will have a north induced pole therefore the other side will have a south...if you use the right hand rule for solenoid...your thumb will be sticking into the page...and you will curl your fingers in the upward direction III With a coil this concept can be better explained.
He is a ver very good teacher.
I use Thumb as V, index finger as B, middle finger as F, and memorize it by saying Very Bad Finger :D
Might use this.
jermiinus
Bo
Lo
@@skmobarakhossion6558 underrated genius
Correct me if I'm wrong but didn't he apply Fleming's right hand rule incorrectly? The wire is moved to the left - that's the thrust. B-Field out of the video, current goes up (which, given that conventional current is opposite to electron flow, means the charge goes down)...
+Basil Mustafa He wrote the +/- signs on the wrong sides of the wire. Magnetic force pushes positive charges up, negative particles down, and this creates a separation between charges ------>> produces electric field E inside the bar: Fe = qE. This is what makes a potential difference in this wire, and the top of the wire should have the higher potential
He explains very well.
But 12 amps on a #36 gauge wire (6.46 ohms on 12 meters of wire) will likely simulate a fast acting fuse.
Sal is a well of knowledge !
Taking my MCAT in 3 days and this is actually helping a ton.
SO COOL!!! That was really interesting. Where have you been for the last 2 years!?!?
I learned this stuff without calc n it was so much more confusing I hate classes where they just give formulas. Also to answer questions in comments. First, it's electrons that move negative to positive but current which points in the direction of force travels positive to negative. As for cross product, it's prob too complicated to learn without taking a linear algebra or vector calc class. for ure level just remember that a cross between two vectors = a vector perpendicular to first 2
bravo!!!!!its best.................
it's sine because sine goes with cross product. cosine goes with the dot product; you're probably getting them confused.
you sir, are a hero. i've checked out your vids SO many times, haha.
Isn't Vec(F)=[Vec(v) cross Vec(B)]Q the formula for the force exerted on a proton in a Mag. field?
Since this is an electron we are talking about, the magnetic force will be exerted in the opposite direction, namely down the wire. So actually, the bottom will become negative, and the top will become positive.
This is the only way it can work, because otherwise, the current induced will be in the same direction as movement of electron (Right hand rule), and that is definitely not possible.
Thanks for the great explanation!
معدل خوش تشرح
An easier way to indicate the direction of the current movement is to use the same gesture as you would to indicate magnetism and current (the right hand rule). So, velocity direction indicated by thumb, back hand indicates direction of magnetic field, and knuckle's point in the direction of flow of the current.
@Khanacademy With all due respect sir, this is the phenomenon of emf generation across a conductor (With the force acting on charges INSIDE a conducting material.) Can you tell me whether we can move a static charge "Electron" present in free space "In Equilibrium" using a disturbed magnetic field
Khan academy is a big reason many of us are still in college. Please don't stop teaching! :))
that was insane dude.
You are a genius! Everything makes sense now!
we all of us here follow your virtualnet class ...so...thanks y.. awesome labor....and y.. particular way o.. teaching Fem magnetics electricity..from lima peru
Bro , are you still alive?
Watch Sal's video on the cross product. The force vector must be perpendicular to the velocity vector and the magnetic field.
I was taught at school that I should use the left hand rule in the situation posed at 3:13. I was told that First finger = Field, seCond finger = Conventional current, and thuMb = Motion (direction of force). If you apply this to this situation you get the same result, since the first finger points out of the screen, the middle finger to the left and therefore the thumb upwards. Is this OK or just a one off?
emf = electro motive force = the force that moves the electron = voltage. Like pressure this force must be a difference (potential difference) or electrons won't move. Most voltages are referenced to zero, but that is not always the case as in a potential divider network of resistances, where the potential difference may between two positive voltages, or between a positive and negative voltage. By positive and negative I imply direction of current flow viz +12 V has the same magnitude as -12V
Basic EM good explanation.
What happens when we use non-intertial reference frames? What do Maxwell's equations become in such a reference frame...?
Thanks a lot. I was wondering what is the mechanism of Induced current. This video just did it for me !!! you Rock Buddy ! x)
i like the drawing of his hand
You are my hero
Can someone help me with this question?
If a current is induced on the wire in the video, what happens to the right hand wrap around rule and the magnetic field?
Because it started out with both sides the magnetic field coming out of the page so once a current is induced, is there a new magnetic field (which would be out of the page on the left of the wire and into the page on the left of the wire)? or would the field stay the same (out of the page on both sides of the wire)
thanks!
a bloody life saver
shouldn't the index finger be pointed in the opposite direction of the velocity? I mean, the current is opposite to the velocity. + to -, not the other way around (eventhough it in reality is the other way around)
God Bless you
my favourite teacher
great jorb
you are awesomeee ! greatest ever teacher on Earth !
nice, you should become my physics teacher @ Lowell High School lol, you're really good at this
Loved it
why isn't the middle finger pointed to the right? if the velocity is to the left, and so is the negative charge, then the current should be to the right, right?!
My teacher says that if a conductor moves with uniform velicity in a uniform magnetic field then the there is no change in magnetic flux... hence no emf is generated....... But from the equation you derived B=lvb voltage(ie.. emf) is being generated even when the wire is moving with constant velocity...........I am confused
Eureka moment- mag field can induce current
He said that if a magnet is brought into motion near the wire then too, the charges start moving. If i am correct, the motion of a charge is required for it to feel the magnetic force and not the variation of the magnetic field?
nice video bud, cheers
I don't get it : /
I mean if the force was going down, it'd still be perpendicular to the magnetic field and the velocity vector. What I'm asking is that if electrons move to the left, then the current is considered to be moving to the right.
Lenz's Law: Any current driven by an induced emf opposes the change that caused it, in other words vemf=-Blv
watch?v=qWu82nJS42I
@BoQuan22
oops I mean into the page on the RIGHT side
this is fucking amazing
thank you
Nailed it
bhai jan kia ap bta sakte he induced current ki applications kon konsi he jaldi
Thats a good looking hand
isn't induced current caused due change in magnetic flux??
if anybody has an answer please do because I'm really confused at the moment.
+Va' Su -- Yeah I thought the strength of the field had be changing over the displacement of the wire for it to induce a current.
induced emf is equal to rate of change of flux linkage, in this case he has changed the area as the wire is moving with a constant velocity, you could have a changing b field, the number of turns of wire or a change in angle.
Ben Sully can you tell me which area has changed?
Geez, his version of the right hand rule is WEIRD! But as long as you get the same answer, sure, go ahead.
what if there wasn't a resistor? will the current be infinity?
where is the video on generators? can't find it
I think this video is made in 2009 and I am watching this video in year 2023 still very helpful a 14 year difference but superb [fun fact I was born in year 2007 ] and this video is of 2009 😂
Doesn't the field have to be changing over the displacement of the wire in order to induce a current?
No, emf = -d(phi(B))/dt. since phi = integral(B*dA), the change in flux is dependent on the area rate of change in a stable magnetic field.
cos 90 is 0, sin 90 is 1.
I could nevr draw a palm that good
What about if there were no 6 Ohm resistor on that wire? How could you find Current (I) from the equation V = IR?
I think you already found out about it, but I'm gonna answer for the people that may watch this video in the future. The answer is, there will always be a resistance on the wire, there is nothing in the world without resistance. If there is no resistance, the current was going to be infinite in theory, but limited by the speed the electrons can travel at no resistance in reality, which depends on the energy you are givig to it (given the situation that the machine we are talking about could provide that much current, but most machines have a limit on how much current they can give), but the power (or the energy used by the wire for heat and stuff) would be 0. Nothing would be lost and 100% of the electrical energy you added to the system would go to the machine you want it to go.
***** absolutely right:)
can l know poregram write that tudy it...
why doesn't the index=B thumb=I middle finger=F work?
thumb would go right (current is opposite to V)
index finger would go out of page
middle finger would go DOWN, I was thought that version of the right hand rule in school
thanks!
edit: after watching videos by other users, it seems that it's an american convention to use velocity instead of current and say that the charge is positive
The only subject missing: mutual induction.
Makes so much sense!!🤓
i want to learn lenz law....can anybody can give me the link?
OK
why in the world is the force going upwards??!!??! if the charges are going left, then the current is going right, right? and if the current goes right, the force should go down
This person must be a mobile version of Google
@coolwierdo WHO YOU?!?!
@behrlich2008 ben! xD
@hetroman He's better. He doesn't come with ads!
ohhh nooooo:( where's the next video??????
where is the next video???
3:43
Focus dude!
Where's the next video? C'mon Sal you're killing me. JK -- thanks for all the help!
He was. Then he escaped and made educational videos.
You never saw me in the next video whats up with that?
thats just kids stuff
easy man so easy
Syed Muhammad Hassan big man
His rule is wrong. The positive charge is supposed to move downwards.
I was wondering if I thought wrong
Would you be able to use a better mic next time? It's easy to understand, but it's painful to have to listen to this for prolonged periods of time
This video is 8 years old.
@behrlich2008 the girl who can't use the urban dictionary loool :D
terrible handwriting, bad colors, decent explanation
where's the next video?