Unit 8 Assignment 1

20. Because the magnetic force which deflects the electrons is defined by F = q * v x B (v x B is the cross product of the 2 vectors), so: The force vector would always be perpendicular to both the v and B vectors.

Since the force is perpendicular to the electron's velocity vector, and thus the path of the electrons, the work done by the field on the electrons is 0, because W = F*d*cos(theta), and theta=90 degrees, therefore cos(theta)=0, and W=0

If W = 0 then there is no change in the kinetic energy of the electrons, thus their speed remains constant; the acceleration provided by the magnetic field was used only to change the direction.
31. Well, it depends upon the Sensitivity setting of the metal detector. As it is clear, the threshold value of the metal detector's sensitivity can be adjusted to suit various needs.

so it is obviously set to discard small variations caused by a very small pieces of metal.
34. Yes, There is nothing seperately as a DC motor or DC generator. It is simply a DC machine. It acts either as a motor or a generator depending on the input. If the input is mechanical energy, the output is electrical : this is generator action If the input is electrical, the output is mechanical torque: this is motoring action
48. when you step up the voltage with transformers you lose current. It is a trade off and motors are not 100% effective so you would have a power loss.

Unit 2 Assignment 1

8. when your car moves along the highway at a constant velocity the net force on it is zero why
Friction, it pulls against the forward motion... The engine must continue to run in order to maintain the constant velocity.

17. If you hold an apple over your head and drop it what are all the the forces acting on it as it drops?
If you hold an apple and drop it then gravity is the only force working on it. If