24. Electric Force & Field; Gauss' Law

A small 1.0 g block charged to 75 nC is placed on a 30° inclined plane. The coefficients of static and kinetic friction are 0.20 and 0.10, respectively. What minimum strength horizontal electric field is needed to keep the block from sliding down the plane?

An electric field E=200,000î N/C causes the point charge in FIGURE P22.68 to hang at an angle. What is θ?

A 0.10 g honeybee acquires a charge of +23 pC while flying.b. What electric field (strength and direction) would allow the bee to hang suspended in the air?

A −12 nC charge is located at (x, y)=(1.0 cm, 0 cm). What are the electric fields at the positions (x, y)=(5.0 cm, 0 cm), (−5.0 cm, 0 cm), and (0 cm, 5.0 cm)? Write each electric field vector in component form.

INT A proton is fired horizontally into a 1.0×10^5 N/C vertical electric field. It rises 1.0 cm vertically after having traveled 5.0 cm horizontally. What was the proton's initial speed?

A −15 nC charge is at x=+2.0 cm on the x-axis. A second charge q is located somewhere on the x-axis to the left of the origin. The electric field at y=2.0 cm on the y-axis is Ē =3.0×105 î N/C . What are (a) the charge q in nC and (b) its distance from the origin?

A thin, horizontal, 10-cm-diameter copper plate is charged to 3.5 nC. If the charge is uniformly distributed on the surface, what are the strength and direction of the electric field (a) 0.1 mm above the center of the top surface of the plate?

Figure 24.32b showed a conducting box inside a parallel-plate capacitor. The electric field inside the box is E (→ above E) = 0 (→ above 0) . Suppose the surface charge on the exterior of the box could be frozen. Draw a picture of the electric field inside the box after the box, with its frozen charge, is removed from the capacitor. Hint: Superposition.

The three parallel planes of charge shown in FIGURE P24.44 have surface charge densities ─ ½ η , η , and ─ ½ η. Find the electric fields EA (→ above E) to ED (→ above E) in regions A to D. The upward direction is the + y-direction.

A 0.80-μm-diameter oil droplet is observed between two parallel electrodes spaced 11 mm apart. The droplet hangs motionless if the upper electrode is 20 V more positive than the lower electrode. The density of the oil is 885 kg/m³ . (c) Does the droplet have a surplus or a deficit of electrons? How many?