A LovattPhysics video explaining the importance and the difference between magnetic flux, flux density and flux linkage and their relationships to magnetic field strength.
I love how a sub-9 minute video explains better on flux, flux density, and flux linkage better than a textbook does in 10 pages ahaha great video my guy
thanks for the best simplified and practical explanation. in the videw it show F=iBL , i read in some different physic book that magnetomotive force F= Ni. can you please give more clarification about what different between this two different formula for F.
from my electromechanic engineering book i have another formula used for the force (Mmf , magnetomotive force), as can be seen from bellow page scan from the book. F= ΦR (where Φ is the magnatic flux, and R is the reluctance) Φ = BA R= l/uA (is is the permeability) so F = Bl/u my question, why are the two formulas not matching (the first formula from your youtube, the second formula from the book)? What did I miss and mistaken? F= ΦR (where Φ is the magnatic flux, and R is the reluctance) Φ = BA R= l/uA (is is the permeability) so F = Bl/u my question, why are the two formulas not matching (the first formula from your youtube, the second formula from the book)? What did I miss and mistaken? And i have to thank you for the awesome and informative video
Thanks! Very clear. Just a quick question. In the last equation, we have 2 variables to find out. Magnetic field (B) and Fi (flux). I have to have one of those to be able to solve the equation as the N and A are easy to be found out. So, how could I work out either of those two variables? Many thanks.
I am working N48 57 x 45 for Eddy Current Brakes . I an using multiple magnets. My question is how to increase my field strength that can be felt at longer distance to influence conductor to produce high eddy current and resultant braking force. Should I stack magnets or place magnets N-S N-S. Or any other orientation you may suggest to benefit from N48 magnets.
So, would you say that two opposing magnets would have a greater magnetic flux density than two magnets that are attracted to one another, at the same distance apart?
It depends where you are measuring the flux density. Directly between the two magnets, there would actually be zero flux when the magnets are repelling (if you google the field diagram you will see what I mean). But when they are attracting there is flux between them. Hope that helps!
One in a billion, A is the area of the plane itself. The plane is usually formed by a coil of wire, so if the wire is coiled in a circle of radius r, A=pi r^2. Hope that helps!
Barney Twist - good question. Magnetic field intensity (otherwise known as magnetic flux density) is basically the same as magnetic field strength - they are two ways of describing the same thing.
Barney Twist yes, you’re right, they should be the same but instead we have Tesla and Weber per sq meter. But try converting each of these units into base SI units and see what you get. They should both give you kg.s^-2.A^-1. So really they are the same, we have just given them 2 different names!
Thank you once again... l did some research sir and l found out that B = μ0H and the unit of μ0 are 1/metres (m^-1) and the units of magnetic field intensity(H) are (wb/m) which is not equal to the tesla (wb/m^2) l am stuck here
Barney Twist sorry I misunderstood your initial question. The H field is not normally taught at IB or A-level to my knowledge so I was confused! I have also done a bit of research now, and to put it simply the difference between H and B fields is that H is dependent on the material the magnet is made from and the material through which the field travels. For example, for two identical magnets in a vacuum H is directly proportional to B and the only difference is the units. If you start to look at the field inside the magnetic material, or if the magnet is inside a material with a different permittivity to a vacuum and that is when you start to see the difference in H. Which course are you studying? I am interested to know where the H field is included in your studies. If you need any more help you can catch me at lovattphysics(at)gmail(dot)com!
@ Naoki Satryo Anggito well if you have the induced or even the initial supplied emf then you may use faradays electromagnetic induction law emf= -N(PHI)/TIME where phi= BA or if its just flux then you dont need N if you want to find the velocity then use emf= -N(PHI)x DELTA SPEED/DELTA DISTANCE
For Flux Density, I don't understand: if, at any point near the proximity of a magnet, there is always a magnetic force acting on an object, why say that there are more of these lines on one area than another? if that were the case, then that would imply that at some points near the proximity of the magnet there would be NO forces at all acting on the aforementioned object.
Good question. Lines are just a visual way of representing the magnetic field. An oversimplification. A more correct way would be to have different shades perhaps, with a darker shade closer to the ends of the magnet, but then you lose the directionality of the field. In Physics there is a lot of simplification in order to make abstract concepts more easy to visualise. Hope that makes sense!
@LovattPhysics I have two N52 Magnets Size 2"L x 1"W x 3/8"H and Magnet wire 18Awg, I will have One Magnet face North and other South But I need to make One Magnet wire Coil that both Magnets rotating 360 degrees in center of One Coil to produce at least 14 Volt and light up 150 watts light bulb, How many turns of magnet wire I need to do or have to produce what i'm looking for the out put. I look forward to your reply
I’m not sure I can answer that without knowing much more details like size of coil, mag field strength, distance from coil to magnet, how the magnet is turning, etc. - my advice would be to start with a small number of turns (eg 10) and measure the output. The output should be directly proportional to the number of turns in the coil so you could calculate it from there. Sorry I can’t be more specific!
Hi, thanks for the comment! Cos vs. Sin is all to do with what our reference angle is. Remember that Cos90 = 0 and Sin90 = 1, Cos0=1 and Sin0 = 0. So in this case, the angle that we're talking about is the angle between the normal to the plane of the coil and the magnetic field lines. If this angle is 0 degrees then the magnetic flux through the coil is at a maximum, so we use Cos, because Cos is at a maximum at 0 degrees too. However, if we were talking about the angle between the field lines and the plane of the coil, then the flux would be highest when this angle was 90 degrees, so we could use Sin. Hope that helps. If you need any more info - I've also replied to your email so we can discuss on there. LP
You have said that B is the magnetic field strength/intensity; which is not correct. B is the magnetic flux density, and H is the magnetic field strength/intensity. Please edit your video, because people may misunderstand or get confused. Thanks. btw, you asked in which course this video is in use to us; personally I'm using it for Electric Machinery course in EE.
Thanks for this - the IB specify the letter B, and that magnetic flux density is equivalent to magnetic field strength, so B is used for both. This is because there is never a consideration of magnets in different mediums at IB level so the permeability is assumed to be constant. Hope that makes sense!
If you're talking about the final problem, the "surface" of area is vertical in the form of the coil, so the normal is horizontal and parallel to the magnetic field direction, cos(0) = 1
