91Ó°ÊÓ

Consider the situation in Figure 13.39. (a) If we double the distance d, by what factor is the force on the point charge due to the dipole reduced? (b) How would the magnitude of the force change if the point charge had a charge of +3Q? (c) If the charge of the point charge were -2Q, how would the force change?

An electron in a region in which there is an electric field experiences a force of magnitude $\mathbf{3}\mathbf{.}\mathbf{7}\mathbf{×}{\mathbf{10}}^{\mathbf{-}\mathbf{16}}\mathbf{}\mathbf{N}$ . What is the magnitude of the electric field at the location of the electron?

What is the approximate radius of the electron cloud of a typical atom? Which of the following charged particles are constituents of ordinary matter? Protons, positrons, electrons, antiprotons, muons

In the region shown in Figure 13.63 there is an electric field due to a point charge located at the center of the dashed circle. The arrows indicate the magnitude and direction of the electric field at the locations shown

2 In the region shown in Figure 13.64 there is an electric field due to charged objects not shown in the diagram. A tiny glass ball with a charge of$\mathbf{5}\mathbf{×}{\mathbf{10}}^{\mathbf{-}\mathbf{9}}\mathbf{C}$placed at location A experiences a force of$\mathbf{(}\mathbf{4}\mathbf{×}{\mathbf{10}}^{\mathbf{-}\mathbf{5}}\mathbf{,}\mathbf{-}\mathbf{4}\mathbf{×}{\mathbf{10}}^{\mathbf{5}}\mathbf{,}\mathbf{0}\mathbf{)}\mathbf{N}$, as shown in the figure. (a) Which arrow in Figure 13.65 best indicates the direction of the electric field at location A? (b) What is the electric field at location A? (c) What is the magnitude of this electric field? (d) Now the glass ball is moved very far away. A tiny plastic ball with charge$\mathbf{-}\mathbf{6}\mathbf{×}{\mathbf{10}}^{\mathbf{-}\mathbf{9}}\mathbf{C}$is placed at location A. Which arrow in Figure 13.65 best indicates the direction of the electric force on the negatively charged plastic ball? (e) What is the force on the negative plastic ball? (f) You discover that the source of the electric field at location A is a negatively charged particle. Which of the numbered locations in Figure 13.64 shows the location of this negatively charged particle, relative to location A?

In Figure 13.66 a proton at location A makes an electric field ${\stackrel{\mathbf{→}}{\mathbf{E}}}_{\mathbf{1}}$at location B. A different proton, placed at location B, experiences a force ${\stackrel{\mathbf{→}}{\mathbf{F}}}_{\mathbf{1}}$. Now the proton at B is removed and replaced by a lithium nucleus, containing three protons and four neutrons. (a) Now what is the value of the electric field at location B due to the proton? (b) What is the force on the lithium nucleus? (c) The lithium nucleus is removed, and an electron is placed at location B. Now what is the value of the electric field at location B due to the proton? (d) What is the magnitude of the force on the electron? (e) Which arrow in Figure 13.65 best indicates the direction of the force on the electron due to the electric field?

You are the captain of a spaceship. You need to measure the electric field at a specified location P in space outside your ship. You send a crew member outside with a meter stick, a stopwatch, and a small ball of known mass M and net charge +Q (held by insulating strings while being carried). (a) Write down the instructions you will give to the crew member, explaining what observations to make. (b) Explain how you will analyze the data that the crew member brings you to determine the magnitude and direction of the electric field at location P.

A sphere with radius $\mathbf{2}\mathbf{}\mathbf{\text{cm}}$ is placed at a location near a point charge. The sphere has a charge of $\mathbf{-}\mathbf{9}\mathbf{×}{\mathbf{10}}^{\mathbf{-}\mathbf{10}}\mathbf{}\mathbf{\text{C}}$ spread uniformly over its surface. The electric field due to the point charge has a magnitude of $\mathbf{470}\mathbf{}\mathbf{\text{N/C}}$ at the center of the sphere. What is the magnitude of the force on the sphere due to the point charge?

What are the magnitude and direction of the electric field $\stackrel{→}{\mathbf{E}}$at location $<20,0,0>\mathbf{cm}$if there is a negative point charge of $\mathbf{1}\mathbf{nC}\left(1×{10}^{-9}C\right)$at location$<40,0,0>\mathbf{cm}$? Include units.

4 A sphere with radius $\mathbf{2}\mathbf{}\mathbf{\text{cm}}$ is placed at a location near a point charge. The sphere has a charge of $\mathbf{-}\mathbf{8}\mathbf{×}{\mathbf{10}}^{\mathbf{-}\mathbf{10}}\mathbf{}\mathbf{\text{C}}$ spread uniformly over its surface. The electric field due to the point charge has a magnitude of $\mathbf{500}\mathbf{}\mathbf{\text{N/C}}$ at the center of the sphere. What is the magnitude of the force on the sphere due to the point charge?