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Question
In an experiment, a student runs a comb through his hair several times and brings it close to small pieces of paper. Which of the following will he observe?
1. Pieces of paper repel the comb.
2. Pieces of paper are attracted to the comb.
3. Some pieces of paper are attracted and some repel the comb.
4. There is no attraction or repulsion between the pieces of paper and the comb.
Solution Video

# OpenStax College Physics for AP® Courses Solution, Chapter 18, Problem 7 (Test Prep for AP® Courses) (0:53)

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Video Transcript
This is College Physics Answers with Shaun Dychko. This comb is charged after running it through the student's hair. And let's suppose it's positively charged. Although we don't know what the charge is, but it doesn't really matter. Let's just suppose it's positive. And these neutral pieces of paper will have an induced polarization caused by the charges on the comb. The electrons on the paper will collect on the side nearest the comb and there will be a force of attraction on these neutral pieces of paper. And the force of attraction is on the comb, too. So this is an induced polarization. The pieces of paper are not charged, but there's a charge distribution. And with negative charges close to the comb being attracted to the comb. So the answer is b.