Honors

Test results were very disappointing. It seems that anything not presented within the last 48 hours is gone.

Many of you have forgotten all we did about circular motion and the meaning of angular speed and how to find angular acceleration. Much of the work we did on orbits in magnetic fields is also gone.

Many of you tried to apply the equation for force on a wire carrying current to a single charge. What was the length you would use.

Despite words on the test and a message on the board and the nature of the picture on the test many of you assumed that the d which was clearly shown as the distance from a wire to the point where you were asked to find the field was the diameter of something and therefore the radius to be plugged into the formula had to be 1/2 of d. This was done after frequent reminders that r was the distance from the point of measurement of the field to the wire creating the field and was called r because the field lines make circles of radius r around the wire.

Almost all of you forgot that the force on a charge in a magnetic field is perpendicular to the velocity and the field. The majority of you do not even know how to find the area of a circle.

Many of you tried to find the field from a single wire by using an equation we developed for solenoids. Where did you get the number of turns from?

Lay a solenoid on its side and h becomes length, right. Most of you got that right and then decided that 15 cm is 15 m. Did you really think the solenoid was 50 feet long?

Not one of you you could turn the flow of charge into a current density. Electrons flowing to the left are a current to the right. The number of moving electrons per cubic meter times the area times the average velocity TIMES THE CHARGE PER ELECTRON gives the current doesn't it? If the area is 1 square meter then then the current density, J, is I/1

You folks will have to decide if we are honors classes this year. Plugging numbers into formulas whose meaning and whose basis for correctness you do not comprehend is not honors work.