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10 (a) A student rubs a plastic comb with a dry cloth to give the comb a positive electric charge - Edexcel - GCSE Physics - Question 10 - 2018 - Paper 1
Question 10
10 (a) A student rubs a plastic comb with a dry cloth to give the comb a positive electric charge. Figure 19 shows the charged plastic comb picking up small pieces o... show full transcript
Worked Solution & Example Answer:10 (a) A student rubs a plastic comb with a dry cloth to give the comb a positive electric charge - Edexcel - GCSE Physics - Question 10 - 2018 - Paper 1
Step 1
Explain how rubbing the comb with a dry cloth gives the comb a positive electric charge.
Answer
When a plastic comb is rubbed with a dry cloth, electrons from the surface of the comb transfer to the cloth. This transfer of electrons occurs due to friction, a process known as triboelectric charging. As electrons are negatively charged, their removal from the comb leaves the comb with a net positive charge. This is because the comb now has more protons (positively charged) than electrons (negatively charged), resulting in the comb becoming positively charged.
Step 2
Explain how the positively-charged plastic comb picks up the small pieces of paper.
Answer
The positively charged comb can attract small pieces of paper due to electrostatic forces. When the comb approaches the neutral pieces of paper, the positive charge on the comb induces polarization in the paper. This means that the electrons in the paper are attracted toward the comb, creating a region of negative charge closest to the comb and a region of positive charge further away. The attraction between the positively charged comb and the induced negative charge on the paper pieces causes the small pieces to be attracted to and picked up by the comb.