Exam 23: Electric Fields

Rubber rods charged by rubbing with cat fur repel each other. Glass rods charged by rubbing with silk repel each other. A rubber rod and a glass rod charged respectively as above attract each other. A possible explanation is that

A point charge Q is placed on the x axis at x = −2.0 m. A second point charge, −Q, is placed at x = 1.0 m. If Q = 60 μC, what is the magnitude of the electrostatic force on a 40-μC charge placed at the origin?

A particle (m = 20 mg, q = −5.0 μC) moves in a uniform electric field of 60 N/C in the positive x direction. At t = 0, the particle is moving 25 m/s in the positive x direction and is passing through the origin. How far is the particle from the origin at t = 2.0 s?

Two imaginary spherical surfaces of radius R and 2R respectively surround a positive point charge Q located at the center of the concentric spheres. When compared to the number of field lines N₁ going through the sphere of radius R, the number of electric field lines N₂ going through the sphere of radius 2R is

Three point charges, two positive and one negative, each having a magnitude of 20 μC are placed at the vertices of an equilateral triangle (30 cm on a side). What is the magnitude of the electrostatic force on one of the positive charges?

A particle (mass = 5.0 g, charge = 40 mC) moves in a region of space where the electric field is uniform and is given by E_x = −2.3 N/C, E_y = E_z = 0. If the position and velocity of the particle at t = 0 are given by x = y = z = 0 and v_z = 20 m/s, v_x = v_y = 0, what is the distance from the origin to the particle at t = 2.0 s?

When gravitational, magnetic and any forces other than static electric forces are not present, electric field lines in the space surrounding a charge distribution show