What is change in the magnetic flux (delta B)?

[Physicsissuef]

What is change in the magnetic flux (delta B)? Like on this http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/emfchb.html"

 

[rock.freak667]

Well the magnetic flux is given by $\Phi=BA$ where B is magnetic flux density and A is the surface area.
So a field interacts with another magnetic field then the value of B changes and hence there should be a rate of change of flux. And by faraday's law, and emf is induced.

 

[Physicsissuef]

Is it like, when I approach magnet, than the magnetic domains of the coil get in line with the magnetic field of the magnet and when I get back the magnet, the magnetic domains of the coil are like in the first position? I mean, for the direction of the magnetic flux.

 

[Physicsissuef]

Can somebody help me to determine the direction of the magnetic flux of the coil?is that, something to do with the aligning of the magnetic domains?

 

[rock.freak667]

Can somebody help me to determine the direction of the magnetic flux of the coil?is that, something to do with the aligning of the magnetic domains?

A coil like a solenoid? if so then to determine the direction of the magnetic flux you need to use the right hand grip rule

 

[Physicsissuef]

A coil like a solenoid? if so then to determine the direction of the magnetic flux you need to use the right hand grip rule

But, I thought in practical way. What happens with the flux?

 

[Physicsissuef]

And can you please explain me this quote from "Newton Ask A scientist"

These days, most hula hoops have beads in them. Let's pretend that if
the beads move inside the hoop they will generate wind through the hoop.
Let's say if they go clockwise, they generate a wind going in the direction
a screw would go if the beads were turning it. Let's say if you increase
the amount of air going in that same direction through the hoop, the beads
will feel forced to move (so far we have Faraday's law) counter-clockwise
(now we've added Lenz's law).

How is it possible that increasing the amount of air will change the direction of the beads?
Here is the whole topic:
http://www.Newton.dep.anl.gov/askasci/phy99/phy99x61.htm