‫Welcome back.
‫So so far, we have covered one application of a cross product, we learned how to compute a moment
‫vector in 3-D using the cross product.
‫However, there is another application and quite interesting, actually.
‫It's in the field of electricity and magnetism.
‫There is a law in physics that states that a force vector equals Q, V, Cross B, and so Q is a charge
‫of a particle.
‫It can be plus some kind of number or minus some kind of number.
‫V is the velocity vector of that particle and B is the magnetic field.
‫So the charge of the particle times, the velocity vector of that particle cross the magnetic field
‫through which that particle goes.
‫A magnetic field is also a vector because it has a magnitude and direction.
‫And so let's create a situation now where an electron flies into a magnetic field, the white crosses
‫our magnetic field vectors pointing into the screen.
‫It's a uniform field.
‫If you look at it from the side, it looks something like this.
‫You see, it's a uniform field and it's the same thing like this.
‫Only now you're looking at it from above, from here.
‫All right.
‫And in red, you have an electron that has a negative charge and the forward velocity vector at time
‫equals zero seconds.
‫So I have an exercise for you based on this formula here.
‫Can you tell me how the electron will move in this magnetic field?
‫What will it trajectory be?
‫You don't have to use numbers.
‫Just tell me the shape of its motion.
‫Try to draw an approximate trajectory for this electron.
‫And I will see you in the next video.
‫Thank you very much.
‫And see you there.