Damn it, PF again erase all of my work

[flyingpig]

Homework Statement

I honestly don't understand why such an advanced forum won't save or let you hit backspace on your work...

The figure below shows a top view of a bar that can slide on two frictionless rails. The resistors is R = 6ohms, 2.50T B-field into the page, l = 1.2m

a) Find the applied force required to move the bar to the right at a constant speed of 2m/s


Solutions

I know that constant speed implies immediately that the magnetic force is to the left, which implies the current must also be counterclockwise. But I don't want to use this method.

I want to know just how can you tell that the induced current is counterclockwise, just how do you know the positive charges will be at the top and the negatives will be at the bottom? If this problem doesn't say constant speed, how do I determine the direction of the induced current?

Should I wrap my hands around the bar (even though it does NOT say it is conducting) and see that the bar produces a current clockwise because of the 2.5T b-field that is directed into the page and by Lenz's law the induced current is counterclockwise?

 

[flyingpig]

Picture looks like this, the black arrows are drawn from another problem, so it isn't reall there

[PLAIN]http://img813.imageshack.us/img813/1065/60582408.png

 

[cristo]

I honestly don't understand why such an advanced forum won't save or let you hit backspace on your work...

It's not the site that won't let you hit backspace, that will be a browser issue.

 

[gneill]

It's not the site that won't let you hit backspace, that will be a browser issue.

Also, when logging in, select the "remember me" box. This seems to prevent sessions from timing out.