AP Physics C E and M 8.3: Fields of Conductors and Insulators

Describe electric fields generated by charged conductors or insulators and connect field behavior to the distribution of charge.

[Maximum number: 1]

An isolated, air-filled, charged capacitor consists of two conducting, coaxial, cylindrical shells

that each have length L. The inner shell has radius $R_{1}$ and the outer shell has radius $R_{2}$ , as

shown in Figure 1, where $R_{1}<R_{2} \ll L$ . The surface charge densities (amounts of charge per unit

area) of the inner and outer shells are $+\sigma_{1}$ and $-\sigma_{2}$ , respectively. The absolute values of the

total charges on the shells are equal.

Figure 1

Note: Figures not drawn to scale.

A.

On the axes shown in Figure 2, sketch a graph of E as a function of r from r=0 to a

position that is outside the outer shell.

Figure 2

(iii) For sketching a graph that is zero for both $0<r<R_{1}$ and $r>R_{2}$

Point A6

For sketching a graph that is decreasing and concave up for $R_{1}<r<R_{2}$

Scoring Note: The curve does not have to intersect the vertical dashed lines for this

point to be earned.

Example Response

Figure 2

All question bank results loaded

8.3.B—Describe the electric field generated by charged conductors or insulators question 1