Difference between magnetic field strength and flux density? - The Student Room
Relationships involving intensity I, flux density F, and flux E of isotropic . the relationship between decreasing solar radiation (or global dimming) and wide. To be more precise, we can write out the full relationship: both the magnetic flux density and the magnetic field strength are examples of a magnetic field. The electric flux ()is defined as the electric field times the normal area vector. In Gausses law this quantity is proportional to the amount of charge enclosed by a.
Air density goes down as you increase altitude. So there's very low density up here. This is in between. I don't have to draw all the air particles, but you get the sense. Lot of air, lot of air down here. And the air is moving. And so let's say that the air, let's say the air is Let me do the velocity vectors in a different color.
So, these are some of the velocity vectors of the air. Let's say the air on this side is moving is moving at let's say, a medium velocity. So right over there. But as we move more in that direction, the air is moving faster. So they have larger velocity vectors like that. We see that in general, all of the air is moving in that general direction, that's the way I'm drawing it. And I can draw the velocity vectors over here. The air is less dense.
But the trend in the velocity vectors, when I go from the left to the right is roughly the same. So that's the flow. Now I'm just sampling some of the velocity vectors there. So let's talk about flux. And the thing about flux, really of any form, you have to think about a surface. So let's imagine you were to put some type of a net. Let's say you were to put a net right over right over here, right over here. And if we think about the flux, we would say, well how much air is traveling through that net in a certain amount of time?
We could say how many molecules are traveling in say, each second. And so this would have some flux associated with it.
Relative to the air. But what if we were to take that same net. And we're assuming it's some type of theoretical net that actually does not impede the air flow. But it helps us visualize a surface.
Electric flux and electric flux density
What if we were to move that net a little bit to the right where the density is the same, but the particles are just moving faster. Well now, our flux would increase. So this is larger flux. Why is our flux increase? Because, well, the density is the same, but in any given amount of time I'm gonna have more things going through that surface.
Now what if I were to put that same net and move it up to this high altitude, right over here? Well, the velocity of the molecules are the same, and they're going in the same direction.
Electric flux and electric flux density
But there's just fewer of them. So you're going to have less fewer molecules traveling through the surface in a given amount of time.
So this is going to have smaller flux. And this is all relative to my first one.
Now, what if you were to take the same net and instead of the direction of the air being perpendicular to the surface, be normal to the surface, what if you were to take the net and reorientate it so that the air is going in the same direction of the surface. So what if you were to take the same net and you were to make it like this. So that it's the same net. I know it doesn't look exactly the same.
But it's the same net, and you're to make it like this. Well now how much air is traveling through that net in a given amount of time? Well now very little to zero air is gonna be traveling through that net in any given amount of time.Electric flux density and relationship between D and E
The air is going along the surface, not through the surface. So this one, let's just say that all the air is going exactly in the same direction as the surface, so nothing is going through the surface.
We would say that this one has zero, zero flux. Now let's say that this theoretical net that actually does not impede the air flow, let's say we can stretch it or contract it. So if we stretch that net, in the same, let's say we were to do it, let's say we were to stretch it up like this.
So it becomes a bigger net. So it becomes a bigger net like this. Well now this thing's gonna have larger flux because there's just more area. There's more to flow through. So now, if you said for this surface, you're gonna have a larger flux because there's just gonna be more air is going to go through that in any given unit of time.
So as you can see, when we think about how much of something just flux in the traditional sense. How much of something goes through a surface in a given unit of time. It depends in this case, the density of the substance. It depends on it's velocity. Both the magnitude of the velocity and the direction of the velocity. We see if we orient the surface or if we oriented the velocity.
It's now easy to calculate the luminous flux F in lumens: Where Iv is the maximum luminous intensity measured in candela cd.
This is an approximation because it assumes that all the power is uniformly distributed inside this cone and that no power is emitted outside. With this approximation, we assume all the flux is uniformly distributed in the specified cone and that there is no radiation outside.
This, of course, is not very accurate. Keep in mind the real figures could considerably off but is the best you can get with just the cone angle.
Intensity (physics) - Wikipedia