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.

 

[rwisz]

As a scientist, it is important to remain calm and collected in the face of frustration. It is understandable to feel frustrated when your work is erased or when you encounter difficulties in understanding a problem. However, it is important to approach the problem with a clear and logical mindset.

In this situation, it is important to first understand the problem and its given conditions. From the figure and information provided, we can see that the bar is in a magnetic field and has a resistor. This suggests that the bar is conducting and can produce an induced current.

To determine the direction of the induced current, we can use Lenz's law which states that the induced current will flow in a direction that opposes the change in magnetic flux. In this case, the bar is moving to the right, so the induced current will flow in a direction that counteracts this motion, which is counterclockwise.

If the problem does not explicitly state constant speed, we can still use this principle to determine the direction of the induced current. We can also use the right-hand rule, where we wrap our fingers around the bar in the direction of motion and our thumb points in the direction of the induced current.

In conclusion, it is important to remain calm and logical when encountering difficulties in scientific problems. By understanding the principles and conditions of the problem, we can approach it with a clear and focused mindset, leading to a successful solution.