Sunday, November 07, 2004

Electricity lesson 5 and 6

ELECTRICITY LESSON 5 - Charging by Induction
Lesson: 5.
Take up Hwk: Discussion Questions c.p. 57, hand in friction lab
Lesson: charging by induction text pg. 184-185
Overhead (video) Halloween activity – Movie – electricity and Halloween?
Hwk: C.P. pg. 64

Charging by Induction
- charging an object without actually touching it -

A charged object will induce a charge on a nearby conductor. In this example, a negatively charged rod pushes some of the negatively charged electrons to the far side of a nearby copper sphere because like charges repel each other. The positive charges that remain on the near side of the sphere are attracted to the rod. If the sphere is grounded so that the electrons can escape altogether, the charge on the sphere will remain if the rod is removed.

The following website is a good resource for more information on charging by induction:

ELECTRICITY LESSON 6 - Charging by Induction
Lesson: 6.
Take up Hwk: Take up Charging by Contact Lab pg. 57 questions on the board
Review concept of charging by induction (overhead)
Complete Lab C.P. pg. 59 –
Homework: answer question with diagram pg. 61

Answers to pg. 57 C.P.:

an object is neutral because there is an equal distribution of protons and electrons
a. electrons should be shown to jump onto the ebonite rod to give it a negative charge. The pithball should be shown to be attracted to the ebonite rod so that the neutral pith attracts to the negative ebonite rod where the electrons repel the pith electrons away but attract the protons
b. Acetate should be shown to have electrons jumping off of it to the paper towel. The pith should have been attracted to the rod in this case because the pith has more electrons than the rod.
a. On to the pith ball
b. out of the pith ball onto the acetate rod
4. a. negatively charged
b. positively charged (or some of the electrons leave the object and therefore make the object less negative)
5. Refer to page 58 in course pack.


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