Conductors and Current

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Section 25.11 Conductors and Current

Activity 25.11.1. Warm-Up.

Suppose you place a positive charge in a cavity inside the conductor below. Sketch a charge diagram for the conductor.

A square conductor with a small square cavity in the bottom right. A positive point charge lies within the cavity. — Figure 25.11.1. A positive charge within a cavity in a conductor.
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Activity 25.11.2. Inside a Capacitor I.

The capacitor shown below is made out of two parallel conducting plates. Initially, \(V = 0\) at point A and \(V = 9 \mathrm{~V}\) at point B.

A horizontal rectangle with point A on the left and D on the right below a second horizontal rectangle with point B on the left and C on the right. — Figure 25.11.2. A capacitor made of two conducting plates.
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(a)

Are the conducting plates in electrostatic equilibrium?

(b)

Sketch a charge diagram for the capacitor.

(c)

Sketch the electric field inside the capacitor.

(d)

Determine the potential at each point.

(e)

Describe all changes in the electric potential as you travel around the path \(A \rightarrow B \rightarrow C \rightarrow D \rightarrow A\text{.}\)

Activity 25.11.3. Inside a Capacitor II.

Suppose you connect the two plates of the capacitor with a third conductor between points A and B, as in the figure below.

A horizontal rectangle with point A on the left and D on the right below a second horizontal rectangle with point B on the left and C on the right. The upper rectangle has positive charge distributed horizontally and the lower rectangle has negative charge distributed horizontally. A uniform downward electric field occupies the space between the rectangles. A vertical rectangle connects points B and A. — Figure 25.11.3. A capacitor made of two conducting plates, with a third conductor.
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(a)

Are the conducting plates in electrostatic equilibrium?

(b)

Describe what you expect to happen physically to the charges (you may want to draw multiple charge diagrams showing the situation over time).

(c)

Give a mechanistic explanation for your expectation based on the electric field or the electric potential.

(d)

As before, describe all changes in the electric potential as you travel around the path \(A \rightarrow B \rightarrow C \rightarrow D \rightarrow A\text{.}\)