Exploring Coulomb’s Law for charged particles

Charge Detector Construction

Fabrication Procedure:

Cut two strips of foil lcm by 4cm (1/3" by 1 1/2") Open out the paperclip to form the shape at right.

Push the hook through the middle of the index card and tape so that it is at right angles to the card.

Lay the two foil strips on top of one another and hang them on the hook by pushing the hook through them. Put this setup inside the jar so that the index card rests on top of the jar opening.

You may want to experiment with fabrication option 2 or 3. (See figures below).

Charge Detector Construction

Charge Detector

Bring various charged objects near the top of the hook (above the index card and observe what happens.

Operation Instructions

What happens if the source actually touches the hook?

Notice what happens to the aluminum strips when the sources are pulled away from the top of the hook.

If the strips do not fall back together, gently touch the hook with your finger.

Jar or glass

Aluminum foil

very tight fit

Fabrication Option #1:

Keep small space between sheets at the bottom.

Press the tops of the Aluminum strips together

Index Card

Aluminum foil

Index Card

very tight fit

fold in half

Press the bend in the Aluminum together

Keep small space between sheets at the bottom.

Jar or glass

Fabrication Option #2:

very tight fit

Press the bend in the Aluminum together

Keep small space between sheets at the bottom.

Fabrication Option #3:

Bend the aluminum strip in half and lay it over the paper clip like a towel on a rack.

Aluminum foil

fold in half

Jar or glass

Fabrication Option #4:

A roll of 3-M Scotch Magic™ Tape, 3/4 inch (2 cm) width. (Don't substitute other brands of tape)    A plastic comb and hair or a piece of wool cloth.

Press enough modeling clay into both film cans to fill them halfway to the top.

Fabrication Procedure:

4 plastic drinking straws with flexible ends2 plastic 35 mm film cans Enough modeling clay to fill the film cans halfway.

Press the inflexible ends of two drinking straws into the clay in each can, and bend the flexible ends to form horizontal arms that extend in opposite directions.

The heights of the straws should be the same.

Extra electrons on the moving object pushed the electrons on the charge detector toward the bottom of the electroscope. The foil leaves at the bottom have a negative charge so they repel each other.

Explanations

The foil leaves at the bottom have a positive charge so they repel each other.

The lose of electrons made the moving object positive and the electrons on the charge detector move toward the top.

Explanations

The foil leaves at the bottom have a positive charge so they repel each other.

The lose of electrons made the moving object positive and the electrons on the charge detector move toward the top.

When either charged object moves away, the electrons in the electroscope redistribute evenly so the leaves fall back down.

The observable behavior is the same, so we do not know what kind of charge was on the moving object.

Extra electrons on the moving object pushed the electrons on the charge detector toward the bottom of the electroscope. The foil leaves at the bottom have a negative charge so they repel each other.

Explanations

The foil leaves at the bottom have a positive charge so they repel each other.

The lose of electrons made the moving object positive and the electrons on the charge detector move toward the top.

But we can state one part of Coulomb’s Law.

The observable behavior is the same, so we do not know what kind of charge was on the moving object.

Extra electrons on the moving object pushed the electrons on the charge detector toward the bottom of the electroscope. The foil leaves at the bottom have a negative charge so they repel each other.

Explanations

“Like charged particles repel each other”

End of Presentation