18.8 Applications of Electrostatics

(a) What is the direction and magnitude of an electric field that supports the weight of a free electron near the surface of Earth? (b) Discuss what the small value for this field implies regarding the relative strength of the gravitational and electrostatic forces.

Earth has a net charge that produces an electric field of approximately 150 N/C downward at its surface. (a) What is the magnitude and sign of the excess charge, noting the electric field of a conducting sphere is equivalent to a point charge at its center? (b) What acceleration will the field produce on a free electron near Earth’s surface? (c) What mass object with a single extra electron will h…

What can you say about two charges $q_{1}$ and $q_{2}$, if the electric field one-fourth of the way from $q_{1}$ to $q_{2}$ is zero?

A frictionless circular track with a diameter of 4.00 m has two spheres of 10.0 kg each anchored very near it. The track is oriented with a diameter along the x-axis. The anchored spheres are just outside the track. One of the anchored spheres is just left of the origin at a distance of $1.00 \times 10^{- 15} \text{m}$ from it, and the other is on the x-axis just right of the track at a distance of $1.00 \times 10^{- 15} \text{m}$ past $\left(4 , 0\right)$. Each sphere carrie…