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coolsday
What is the similarties and differences among electrostatics, gravitational and magnetic forces?
I'm a little busy, but I'll give you suggestions. Look at the form of their equations. Think; is does this force depend on some sort of polarity?
what do you mean by polarity?
and is the magnetic force equation F=BILsintheta?
I mean things like like charges repel, opposite charges... like poles repel, opposite poles... matter.... err.... uhh... yeah. That sort of thing!
There are lots of equations for magnetic force! It depends on what you look at the magnetic force of! Most importantly, does it look like the equations for electrostatic and gravitational forces?
Hey, can you help me with a question?
Right! :) How do the electrostatic and gravitational forces compare to each other though? :) Maybe... I'm getting distracted from my own homework, but I should focus... It doesn't hurt to post it anyway!
the electrostatic forces and gravitational forces are similar in equation except for their constants. They increase with a direct proportion of their masses and decrease inversely with the distance squared. However, electrostatic forces can attract and repel while gravitational forces can only attract. Is there anything else?
I think that's great! I would specify "direct proportion of \(\sf the\ product\ of\) their masses," just to be picky.
how about "forces vary directly with the product of the charges/masses"?
Right! Throw in that distinction between gravitational and electrostatic.
Maybe say "decrease directly" or something.. What wording is proper confuses me sometimes. You could get away with directly proportional to the product of masses for gravitational and charges for electrostatic and inversely proportional to the square of the length of separation or something like that.
ok thanks. Can you help me with another one? A horizontal 6 m long wire that runs from west to east is in a 0.03 T magnetic field with a direction that is northeast. If a 4.5 A current flows east through the conductor, then what is the magnitude and direction of the force on the wire? I found the magnitude to be 0.5 N but how would i find the direction of the force?
I'll just trust your magnitude, because I forget the equation for current. I think you posted it above, though. Anyway.... The right hand rule! Take your right hand, fingers outstretched. Point it in the direction of the current. Now curl your fingers so that they align with the magnetic field, but don't move your palm. Stick your thumb out. Your thumb points to the direction of the force.
Actually, opposite. That is because of the cross product. \(\vec x\times\vec y=\vec z\) in our coordinate system, so I remember that. For the magnetic force on a moving charge, its \(q\vec v\times\vec B=\vec F\) where \(\vec v\) is the velocity and \(\vec B\) is the magnetic field.
Wait, not opposite, I was right, I think :)
I'm pretty sure I'm right :) All but positive.
would the magnetic field be like this |dw:1398305079394:dw|
Yep. If north is up and east is right, you're correct.
So the current would be to the right.
The current, when considered "conventional current," is the flow of positive charge.
ok, so the force would be perpendicular to both the current and magnetic field?