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When you push the "add current" button, current-carrying wires are added to a region of space with a uniform magnetic field to form a plate carrying current either out of the screen or into the screen (position is given in centimeters and the magnetic field strength is given in millitesla). Restart.

1. Before you add the current, draw an Amperian path that makes use of the symmetry of the field. What is the value of the path integral?
2. Add the current. Draw a path that encloses a number of wires and use this path to find the current per unit length along the x axis (i.e., if you think of the plate as made up of the wires you see in cross section, how much current is carried on the wires from x = 0 cm to x = 1 cm?). Ignore edge effects.

Problem authored by Melissa Dancy and Wolfgang Christian.