Question

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unit 3: electricity
lesson 3.2 conductivity & charging by friction
homework

1. draw a neutral balloon with 5 negative charges.
2. draw a positively charged balloon and a negatively charged balloon.
3. draw 5 positive and 5 negative charges on each of the following - hair and a polyester shirt.
4. which item likes to hold onto its electrons more - the polyester shirt or the human hair?
5. show how charges were transferred if the shirt was rubbed on the human hair.
6. plastic playground slides are made of polyethylene. using the electrostatic series table above, explain why your hair stands up if you put it close to one of these slides that you have just slid down.

Explanation:

Step1: For question 1

Draw a balloon shape. Mark 5 small - sized negative charge symbols (e.g., -) on it to represent 5 negative charges while the overall balloon is neutral, meaning there should also be 5 positive charges not explicitly mentioned in the instruction but implied for neutrality.

Step2: For question 2

Draw two separate balloon shapes. On one balloon, mark positive charge symbols (e.g., +) to represent a positively - charged balloon. On the other balloon, mark negative charge symbols (e.g., -) to represent a negatively - charged balloon.

Step3: For question 3

Draw a representation of hair and a polyester shirt. On each of them, mark 5 positive charge symbols (+) and 5 negative charge symbols (-).

Step4: For question 4

Polyesters have a higher affinity for electrons compared to human hair. This is based on the triboelectric series which ranks materials according to their tendency to gain or lose electrons during contact.

Step5: For question 5

When the polyester shirt is rubbed on human hair, electrons are transferred from the hair to the shirt. The hair becomes positively charged due to the loss of electrons, and the shirt becomes negatively charged due to the gain of electrons. You can show this transfer with arrows pointing from the hair to the shirt.

Step6: For question 6

Polyethylene, of which the plastic slides are made, has a high affinity for electrons. When you slide down the polyethylene slide, electrons are transferred from your body (including hair) to the slide. Your hair then becomes positively charged. Since like - charges repel, the individual strands of hair stand up as they repel each other.

Answer:

1. Draw a balloon with 5 negative charges (and implied 5 positive charges for neutrality).
2. Draw one balloon with positive charges and another with negative charges.
3. Draw hair and a polyester shirt with 5 positive and 5 negative charges on each.
4. Polyester shirt.
5. Electrons transfer from hair to shirt, hair becomes positive, shirt becomes negative.
6. Electrons transfer from hair to polyethylene slide, hair becomes positively charged and strands repel each other causing hair to stand up.