Magentic Fields Flashcards
If they say draw the MAGNTIUDE of emf from a flux linkage graoh remember what to do
Discard the minus sign as its MAGNITUDE
They might give extra info, remember what is change of flux, watch out they give flux instead of flux density!
Yeah si flux = BA, but if they give flux no need to calculate anything else!
Why can overhead cables carrying AC current not be able to float, due to the FIRCE experienced by motor effect with earth magnetic field
Thidnjs bevause it’s AC CURRENT, so as current moves in oppsite directions, while it potentially could balance the weight at one instance, the force would be acting in anotehr oppsite direction the next instant so csnt
Remember when leaving ratios, how to leave the answer as
Try leave not in fractions, right ine as 1 so it’s something :1
If a loop of wire has current going one way then another, why is the FIRCE resuktsnt due to magnetic field 0?
This is because the force acts on BITH SIDES of the wire, and thus they cancel out
Why if current going both ways on loop will there be no resuktsnt force due to msg field o
Because force acts in two different directions due to current in two different ways
Remmeber that the T does not depejd on the velocity of the particle circular motion innmag field
Why not when clearly v = omega r so surely changing v will change t ?
Need ti equate what v actually equals in the scenarior, and then cancel down
If there is no v left over, then it means in THAT SCENARIO only v isn’t there, but might be in others
Always equal equation and then rearrange for T, not T first because it has to be specific to that equation
When asking about describe the motion of s particle bs circuskr or parabolic, what to make sure to include into the wuestionnasnwer
Must be in context, so say INSIDE THE PLANE OF PAPER, or into the plane out of
Also if the field direction isn’t specified, why for magentic is is it still circular, but for electric it could be parabolic going in OR out of the plane of paper?
Because wherever the magentic field acts the force still perpendicular tieards centre , the centre will be different but still a circle in thr plane
But for electric I’d the field is this way or that way it will parabolic into or out of the plane of paper
When using a magnet to make a stationary wave , why is it more efficient and thr amplitude is higher when putting it at the ANTINODE instead of the node
Because putting it at the node, on the left and right of the node the string is trying to go in different ways, but the force ALWAYS acts in one way
- as a result , this is actually taking energy OUT IF THE SYSTEM, with force being negated by whatever stationary wave is doing, as when stationary wants to go down force is up on one side, reducing how far it can go, so amplitude smaller
However placing it at the ANTINODE
- the string di only going in one direction at any time, so this can MATCH WITH THE FORCE, and thus maximum energy transfer is given, instead of force trying to go against the way the stationary is trying to go
This way, we get more effeicny and thus higher energy and so amplitude higher too!
What to know about A level about flux and how it changes WITHIN A MAGNET and with different magnet systems
Everywhere in a given magnet will have same flux
This because flux is inherent priority if magnets thinking about the number of lines which are CONSERVED
- different places will have different density as area changes
- any magnet will have a cinstsnt number if field lines hence flux is the same , as MAGENTIC flux is the NUMBER OF FIELD LINES
Flux is the inherent property, not density, and for any given magent , the flux in the entire magent is the same!
2) But fi make the magnet BIGGER, the flux will increase, but still WITHIN THE MAGNET THE FLUX STAYS THE SAME!!
Reason for why flux in a magnet same magnet is the same!
Because every given magnet will have a cinstsnt number of field lines, and as field lines is flux, the flux in any given magent anywhere is the same
