Physics 212

Activity CM-15

Open a Word file
sure the names of

Software hints:

Computer Intensive Physics

Fall, 1997

Magnetic Fields

Assigned: Day 15, Oct. 16, 1997

Be

You will be using the EM Fieldsoftware.
magnetic fields surrounding long straight wires.

This time, you will be investigating

From the "Sources" menu, choose "2D line currents". As before, the sources we
wish to use will appear at the bottom of the screen. The best way to think of these sources
is to consider them to be wires coming straight out of the screen. These wires have
electric currents flowing through them. The amount of current is indicated by the
numbers on the circles, where "2A" means 2 Amperes.

You may want to show the grid and constrain to grid as well.
click on it and drag it into the middle of the screen.

To place a current,

Begin by placing a large current in the center of the grid. Decide if you want to
display field vectors or field lines. You can make your choice under the "Field &
Potential" menu.

Investigate the magnetic field vectors surrounding a long wire

1. How does the magnetic field strength depend on distance from the current? Justify
   your answer. In addition, you may chose to include one graphic to aid your
   description. Can you write a mathematical equation relating field strength to
   distance from a coil for your data?

2. How does the magnetic field strength depend on the size of the current? Justify your
   answer. In addition, you may chose to include one graphic to aid your description.

3. Based on your study, describe a rule you can use to predict the direction of the field in
   relation to the current.

4. Describe thefield lines surrounding a long straight wire.

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