Holt Physics 17-1 Concept Review worksheet on electric charge, including diagrams and questions about charge transfer and distribution.

Problem Analysis:

The problem involves understanding the behavior of electric charges when a charged object (a red rod) is brought near or in contact with uncharged objects (spheres). The goal is to determine how charge is distributed in each experiment and explain the phenomena observed.

#### Given Information:
1. A plastic rod is rubbed with wool, making it negatively charged.
2. Three experiments are conducted using uncharged metal spheres.
3. The rod is used to influence the charge on the spheres in different ways.

#### Experiments:
- Experiment A: The rod is brought near an uncharged sphere but does not touch it.
- Experiment B: The rod touches the uncharged sphere.
- Experiment C: The rod is brought near an uncharged sphere, then removed.

#### Questions:
1. In which experiment(s), A, B, or C, was negative charge transferred?
2. For each experiment, describe how the charge is distributed on the spheres.
3. In which experiment(s) did polarization occur?
4. What happened to the excess charge on the rod after it was returned in experiments A and C?

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Solution:

#### Step 1: Understanding Charge Transfer and Polarization
- Charge Transfer: Occurs when two objects come into direct contact, allowing electrons to move from one object to another.
- Polarization: Occurs when a charged object induces a separation of charges in an uncharged object without physical contact. The uncharged object develops opposite charges on its near and far sides relative to the charged object.

#### Step 2: Analyzing Each Experiment

##### Experiment A: Rod Near Sphere (No Contact)
- The rod is negatively charged and is brought near the uncharged sphere.
- The negative charge on the rod repels electrons in the sphere, causing them to move to the far side of the sphere.
- This results in the near side of the sphere becoming positively charged, and the far side becoming negatively charged.
- Key Point: No charge is transferred; only polarization occurs.

Charge Distribution:
- Near side of the sphere: Positive charge
- Far side of the sphere: Negative charge
- Total charge on the sphere remains zero (uncharged).

##### Experiment B: Rod Touches Sphere
- The rod is negatively charged and comes into direct contact with the uncharged sphere.
- Electrons from the rod flow onto the sphere, neutralizing some of the positive charges on the sphere and leaving it with an overall negative charge.
- Key Point: Charge is transferred from the rod to the sphere.

Charge Distribution:
- The sphere acquires a net negative charge due to the transfer of electrons from the rod.
- The rod loses some of its negative charge as electrons are transferred to the sphere.

##### Experiment C: Rod Near Sphere, Then Removed
- The rod is negatively charged and is brought near the uncharged sphere.
- Similar to Experiment A, the rod induces polarization in the sphere.
- However, when the rod is removed, the induced charges on the sphere return to their original positions, and the sphere becomes uncharged again.
- Key Point: No charge is transferred; only temporary polarization occurs.

Charge Distribution:
- While the rod is near the sphere:
- Near side of the sphere: Positive charge
- Far side of the sphere: Negative charge
- After the rod is removed: The sphere returns to being uncharged.

#### Step 3: Answering the Questions

1. In which experiment(s), A, B, or C, was negative charge transferred?
- Answer: Experiment B.
- Explanation: In Experiment B, the rod directly contacts the sphere, allowing electrons (negative charge) to transfer from the rod to the sphere.

2. For each experiment, describe how the charge is distributed on the spheres.
- Experiment A:
- Near side: Positive charge
- Far side: Negative charge
- Total charge: Zero (uncharged).
- Experiment B:
- Sphere: Net negative charge (due to transferred electrons from the rod).
- Experiment C:
- While near the rod:
- Near side: Positive charge
- Far side: Negative charge
- After the rod is removed: Uncharged.

3. In which experiment(s) did polarization occur?
- Answer: Experiments A and C.
- Explanation: Polarization occurs when a charged object induces a separation of charges in an uncharged object without physical contact. This happens in both Experiment A and Experiment C.

4. What happened to the excess charge on the rod after it was returned in experiments A and C?
- Answer: In both experiments A and C, the rod retains its excess negative charge because no charge transfer occurred.
- Explanation: Since there was no physical contact between the rod and the sphere in these experiments, the rod's charge remained unchanged.

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Final Answers:

1. Experiment B
2.
- Experiment A: Near side: Positive, Far side: Negative, Total: Zero.
- Experiment B: Sphere: Net negative charge.
- Experiment C: While near: Near side: Positive, Far side: Negative; After removal: Uncharged.
3. Experiments A and C
4. The rod retained its excess negative charge in both experiments A and C.

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