1D Charging By Contact (fall 13).notebook
April 08, 2015
Learning Goal
Today I will be able to describe two different ways that an object can be electrically charged.
Charging By Contact
There are three different methods we can use to charge objects. Two involve bringing objects into contact with each other.
#1 ­ Friction
As we've discussed already, when two different objects are rubbed together, one will gain electrons and one will lose electrons.
1D Charging By Contact (fall 13).notebook
April 08, 2015
Example #1
Using the electrostatic series on pg. 473, complete the following table:
materials
positive
negative
cotton and vinyl
amber and rabbit fur
acetate and paper
silk and silk
Activity #1
Charge an ebonite rod with rabbit fur. Check that it is charged by placing the rod near a pithball electroscope. What type of charge does the ebonite rod have?
Charge an acetate rod with plastic. Check that it is charged. What type of charge does the acetate rod have? 1D Charging By Contact (fall 13).notebook
April 08, 2015
#2 ­ Conduction
+ ­
­+
+­
­ +­ ­ ­­ +
­ ­ ­
If we bring a charged rod near a neutral pith ball, the objects will attract.
As the rod is brought close, the electrons in the pith ball are repelled to the other side.
­ +
­­+ +
­ +­ ­ ­­ +
­ ­ ­
The positive side of the ball is attracted to the negative rod. This is called an induced charge.
1D Charging By Contact (fall 13).notebook
April 08, 2015
If the objects are allowed to touch, some of the excess electrons in the rod will move into the pith ball.
­­ ­
+ ­ ­ ­
­ + ­+ ­ ­ +
+­
The extra electrons in the pith ball give it a negative charge.
­­
+
­ ­ +­
+­
­ +­ ­ ­­ +
Both objects now have the same charge.
1D Charging By Contact (fall 13).notebook
April 08, 2015
Activity #2
Touch a neutral pith ball with a negatively charged ebonite rod. How will you know when the pith ball has been given a negative charge?
Touch a neutral pith ball with a positively charged acetate rod. How will you know when the pith ball has been given a positive charge?
1D Charging By Contact (fall 13).notebook
April 08, 2015
The third method of charging is called induction. We'll learn about that tomorrow.
Homework
pg. 477 #3­5, 7, 8
1D Charging By Contact (fall 13).notebook
April 08, 2015