For Physics we had to build a simple DC motor, you know the one with copper wire wrapped around an armature, and two bar magnets which create the magnetic field. My question is, how is it that moving the magnets closer to the motor increase the RPM of the motor. I know that there is a crazy RPM formula involving magnetic flux which states that as magnetic flux increases RPM decreases, but that means that magnetic flux gets smaller as the magnets gets closer. is that true?? also I‘m really confused on magnetic flux in general. so if you could just tell me so the magnets getting closer affect the RPM I will give you best answer and what not thanks in advance.
Really this needs a diagram but I'll try explaining without one. You can represent a magnetic field in terms of 'lines of flux'. However the strength of the magnetic field is represented by the flux DENSITY - the more packed together the lines are, the higher the flux density, so the stronger the field. On a diagram, you can think of the field strength as being represented by the number of lines per cm?, though we are really dealing with 3dimensions, so this is not the true situation. 'magnetic flux density' basically means how strong the field is. It is not the same as the 'magnetic flux' (which equals flux density x area) which is simply the number of lines. If you have 2 magnets a long way apart the field midway between them is weak because the lines of flux have spread out and the flux density is small If you have the same 2 magnets close, the field midway between them is stronger because the lines of flux are more closely packed - the flux density is larger. The force (torque to be more accurate) making the coil turn depends on the strength of the field. A stronger field produces more torque so the closer magnets make the coil spin faster.
