Exam 19: Electric Charges, Forces, and Fields

FIGURE 19-1 -Three equal charges are at three of the corners of a square of side d. A fourth charge of equal magnitude is at the center of the square as shown in Figure 19-1. Which of the arrows shown represents the net force acting on the charge at the center of the square?

A particle with a charge of 4.0 μC has a mass of 5.0 × 10^-3 kg. What electric field directed upward will exactly balance the weight of the particle?

FIGURE 19-11 -Three equal point charges of varying signs are placed on three of the corners of a square of side d as shown in Figure 19-11. Which of the arrows shown represents the direction of the net electric field at the vacant corner of the square?

Thirty microcoulombs of NEGATIVE charge experiences an electrostatic force of 27. mN. What is the magnitude and direction of the electric field?

The electric field is continuous.

An atomic nucleus has a charge of +40e. An electron is 10^-9 m from the nucleus. What is the force on the electron?

Electric charge is quantized.

An electron is held up against the force of gravity by the attraction of a fixed proton some distance above it. How far above the electron is the proton?

FIGURE 19-2 -Four point charges of equal magnitudes but with varying signs are arranged on three of the corners and at the center of the square of side d as shown in Figure 19-2. Which of the arrows shown represents the net force acting on the center charge?

A neutron is approximately twice as heavy as the electron.

A 1.0-C charge is 15 m from a second charge, and the force between them is 1.0 N. What is the magnitude of the second charge?

A point charge Q = 7.00 × 10^-9 C is placed at the origin of an xy-coordinate system. What is the electric field intensity E at a distance of x = 30 cm from this charge? (Use k = 9 × 10⁹ Nm²/C².)

A charged particle traveling along the +x axis enters an electric field directed vertically upward along the +y-axis. If the charged particle experiences a force downward because of this field, what is the sign of the charge on this particle?

Figure 19-13 shows four Gaussian surfaces surrounding a distribution of charges. Which Gaussian surfaces have no electric flux through them?

Three point charges are placed on the x-axis. A charge of +2.0 μC is placed at the origin, -2.0 μC to the right at x = 50 cm, and +4.0 μC at the 100 cm mark. What are the magnitude and direction of the electrostatic force which acts on the charge at the origin?

FIGURE 19-15 -A uniform electric field with a magnitude of 6 × 10⁶ N/C is applied to a cube of edge length 0.1 m as shown in Figure 19-15. If the direction of the E-field is along the +x-axis, what is the electric flux passing through the shaded face of the cube?

FIGURE 19-4 -Four point charges of equal magnitude and sign are arranged on three of the corners of the square of side d as shown in Figure 19-4. Which of the arrows shown represents the net force acting on the charge at the upper right hand corner of the square?

Electric field lines and equipotential lines meet perpendicular to one another.

A 5.0-C charge is 10 m from a small test charge. What is the magnitude and direction of the electric field at the location of the test charge?

FIGURE 19-14 -Three point charges of magnitude +2.0 μC, +3.0 μC, +4.0 μC are located at the corners of a triangle as shown in Figure 19-14 The resultant force acting on the +4.0 μC charge is given by