Chapter 23: The Electric Field

Two parallel plates$1.0cm$apart are equally and oppositely charged. An electron is released from rest at the surface of the negative plate and simultaneously a proton is released from rest at the surface of the positive plate. How far from the negative plate is the point at which the electron and proton pass each other?

Two $2.0-cm$diameter disks face each other, $1.0mm$apart. They are charged to $\pm 10nC$.

a. What is the electric field strength between the disks?

b. A proton is shot from the negative disk toward the positive disk. What launch speed must the proton have to just barely reach the positive disk?

Honeybees acquire a charge while flying due to friction with the air. A $100mg$bee with a charge of $+23pC$experiences an electric force in the earth’s electric field, which is typically $100N/C$, directed downward.

a. What is the ratio of the electric force on the bee to the bee’s weight?

b. What electric field strength and direction would allow the bee to hang suspended in the air?

An electron traveling parallel to a uniform electric field increases its speed from $2.0\times {10}^{7}m/s\mathrm{to}4.0\times {10}^{7}m/s$ over a distance of $1.2cm$. What is the electric field strength?

The surface charge density on an infinite charged plane is $-2.0\times {10}^{-6}C/m^2$ . A proton is shot straight away from the plane at $2.0\times {10}^{6}m/s$. How far does the proton travel before reaching its turning point?

The electric field strength $10.0cm$from a very long charged wire is $2000N/C$. What is the electric field strength $5.0cm$ from the wire?

What are the strength and direction of the electric field at the position indicated by the dot in FIGURE$\mathrm{EX}23.3$$?$Specify the direction as an angle above or below horizontal.

Rank in order, from largest to smallest, the electric field strengthsE1 to E4 at points$1\text{to}4$ in FIGURE Q23.3. Explain.

An electron in a vacuum chamber is fired with a speed of $8300km/s$toward a large, uniformly charged plate $75cm$ away. The electron reaches a closest distance of $15cm$ before being repelled. What is the plate’s surface charge density?

A $1.0-mm$-diameter oil droplet (density role="math" localid="1649088632675" $900kg/m^3$ ) is negatively charged with the addition of $25$ extra electrons. It is released from rest $2.0mm$ from a very wide plane of positive charge, after which it accelerates toward the plane and collides with a speed of $3.5m/s$. What is the surface charge density of the plane?