AP Physics C E and M 8.3: Electric Fields

A nonconducting rod of uniform positive linear charge density is near a sphere with charge -2.0 nC. The rod and sphere are held at rest on the x-axis, as shown in Figure 1. Equipotential lines and positions A, B, C, D, and E are labeled. Adjacent tick marks on the x-axis and the y-axis are 0.40 m apart.

Indicate the direction (not components) of the net electric force exerted on the test charge immediately after the test charge is released from rest.

+x +y Directly away from the sphere -x -y Directly toward the sphere

Without using equations, justify your answer using physics principles.

The sphere and the test charge are removed. The rod has length 4 L and uniform positive linear charge density $+\lambda$. The rod is held at rest on the x-axis in the orientation shown in Figure 3. Position P (not shown) is located on the x-axis a distance $x_{\mathrm{P}}$ from the origin, where $x_{\mathrm{P}}>4 L$.

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.

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.