Electric Fields

Mapping

Electric Fields

• Does an electron loose it’s charge if it’s the only charge around?

Electron

Electric Fields

• Does an electron loose it’s charge if it’s the only charge around? No. The charge is still there, even if there’s no other particle for it to interact with.

Electron

Electric Fields

• Charged objects have what is called an Electric Field around them. It works kind of like a piece of stinky cheese…

Electric Fields

• If you are far away, you hardly smell it at all…

Electric Fields

• As you get closer, the smell gets stronger, and stronger, and stronger…

Electric Fields

• As you get closer, the smell gets stronger, and stronger, and stronger…

Electric Fields

• As you get closer, the smell gets stronger, and stronger, and stronger…

Electric Fields

• As you get closer, the smell gets stronger, and stronger, and stronger…

Electric Fields

• What an Electric Field does:

It tells you what would happen if another

charge came nearby (without having to actually do it)

Drawing Electric Fields

• We will describe Electric Fields using pictures, called Electric Field Diagrams.

• You only need to remember one thing:

W.W.P.D.

Drawing Electric Fields

•W hat•W ould• P rotons• D o?

Imagine we have a negatively charged object:

-q

Drawing Electric Fields

• What would a proton do if we were to “drop” one here:

-q

Drawing Electric Fields

• It would go that way

-q

Drawing Electric Fields

• What about if we drop another one here:

-q

Drawing Electric Fields

• It would go that way:

-q

Drawing Electric Fields

• What if we drop some more all around:

-q

Drawing Electric Fields

• They would do this:

-q

Drawing Electric Fields

• The red lines are the Electric Field Map:

-q

Electric Field Map Rules

• To draw a good map, you want at least 8-10 arrows.

• If you object is negatively charged, the arrows go in (WWPD)

• If the object is positively charged, the arrows go out (WWPD again)

Example

• We looked at a negative object, lets look at a positive object:

• Start out with 8 lines without arrowheads:

+q

Example

• In this new case, WWPD?• Go toward or away from the charge?

+q

Example

• Now add the arrowheads in:

+q

Example

• If the charge gets bigger, the arrows get longer:

+5q

Multiple Charges

• What if you have something like this:

+q-q

Multiple Charges

• Or this?

+q+q

Exploration

• Complete the worksheet on Electric Field Maps.

• Do the best you can, remember WWPD.

• Check your answers on the computer simulation.