Magnetic Force from the Lorentz Force Law 从洛仑兹力到磁力

[evamber01]

isn't the direction given by the left hand rule? So you can compare your fingers with the velocity, you catch the arrows of B in the palm of your hand and your thumb can be compared with the direction of the force?

[ReminiscenceHr]

If the angle between the vectors of the point charge velocity and the magnetic field would be 180 degrees (the vectors are antiparallel), does that mean that Lorentz force on that charge would be equal to zero, that is would Lorentz force alter the speed of the charge?

[FPLfree]

THX!!!

[applesilk]

Thanks for comment.

Yes, it does move "in circle" as you mentioned (within the magnetic field B only).

Yes, since it moves "in circle" then the direction of V is definitely changed.

Yes, it's because the magnetic field presents there, but not "magnetic field changes", the direction and amplitude of magnetci field B are fixed in this scenario

[applesilk]

The magnetic portion of a complete Lorenz Law this is F=qvxB (F,q,B are all vectors, they have both magnitude and direction)

Notice the "x" between "v" and "B" in the formula, it's called "cross product" (dot product gives you a scalar and the cross product gives you a vector). So the result F is still a vector

[applesilk]

The reason why the charge is moving "in circle", inmaging you are walking straight on the road, your friend keep pulling your right arm with constant force (which should be strong enough to make you move), are you still able to walk straight?

Same situation applied here, once the charge start to move in B,then according to Lorenz Law, there is a force "which is PERPENDICULAR to BOTH v direction and B direction"

[applesilk]

this PERPENDICULAR forece changes the direction of the charge, hence it moves "in circle".

I hope this can be a bit helpful...

[Rill905]

i thought it was F=q(E+vxB)

[ManoJow2]

Thanks a lot.

My doubt is why the moving charge moving in circle... is that because the magnetic field changes the direction of the V or because the magnetic force does it?

I asked that because it was supposed to go straight, but the direction changes. So that's my doubt, why the direction of the V is changed in this case.

Thanks again!

[freestylesphynx]

Thank you, that was useful.

[applesilk]

You are welcome :)