Exam 21: Electric Charge

Two particles, each with charge Q, and a third particle, with a charge q, are placed at the vertices of an equilateral triangle as shown. The total force on the particle with charge q is:

A charge Q is spread uniformly along the circumference of a circle of radius R. A point particle with charge q is placed at the center of this circle. The total force exerted on the particle q can be calculated by Coulomb's law:

An electroscope is charged by induction using a glass rod that has been made positive by rubbing it with silk. The electroscope leaves:

The charge on a glass rod which has been rubbed with silk is called positive:

Two particles, X and Y, are 4 m apart. X has a charge of 2Q and Y has a charge of Q. The force of X on Y:

Two electrons (e₁ and e₂) and a proton (p) lie on a straight line, as shown. The directions of the force of e₂ on e₁, the force of p on e₁, and the total force on e₁, respectively, are:

Charge is distributed uniformly on the surface of a spherical nonconducting shell. A point particle with charge q is inside. The electrical force on the particle q is least when:

Two protons (p₁ and p₂) and an electron (e) lie on a straight line, as shown. The directions of the force of p₁ on e, the force of p₂ on e, and the total force on e, respectively, are:

In the Rutherford model of the hydrogen atom, a proton (mass M, charge Q) is the nucleus and an electron (mass m, charge q) moves around the proton in a circle of radius r. Let k denote the Coulomb force constant (1/4 $\pi$$\varepsilon$ ₀) and G the universal gravitational constant. The ratio of the electrostatic force to the gravitational force between electron and proton is:

The leaves of a positively charged electroscope diverge more when an object is brought near the knob of the electroscope. The object must be:

To what types of electrically charged objects does Coulomb's law apply?

Two identical conducting spheres A and B carry equal charge and exert electrostatic forces of magnitude F on each other. They are separated by a distance much larger than their diameters. A third identical conducting sphere C is uncharged. Sphere C is first touched to A, then to B, and finally removed. As a result, the electrostatic force between A and B becomes: