Exam 25: Electrostatic Potential and Energy

Two concentric conducting spherical shells have radii r and R (> r) and charges q and Q, respectively. The electric potential just outside the surface of the shell of smaller radius is proportional to

Two identical conducting spheres are placed a distance d from each other and have initial charges of -2Q and 8Q, respectively. The spheres are initially connected by a thin conducting wire; the wire is then removed. The charges on the spheres after the removal of the wire are

Four small spheres, each of mass m, connected by four nonconducting strings to form a square with side d, are placed on a horizontal, nonconducting, frictionless surface. Balls A and B, placed on adjacent corners, each have a charge Q; balls C and D are uncharged. The maximum speed of balls C and D after the string connecting balls A and B is cut is

The electric field in a region is nonzero. The statement that most precisely describes the electric potential in that region is

Work is done on a charged particle to move it a distance d in a uniform electric field E, as shown in the figure here. The particle is

If the electrostatic potential at a point P is negative, then

A charge +q₁ is brought to a point a distance r₁ from a charge +q. Then +q₁ is removed and a charge +4q₁ is brought to a point a distance 2r₁ from +q. If the electrostatic potential at r₁ is V, the electrostatic potential at 2r₁ is

The electric potential due to a dipole at a point situated at a distance r, larger than the distance between the dipole's charges, varies as

A uranium nucleus fissions in two spherical fragments of charge 38e and 54e and radii 5.5 * 10^-15 m and 6.2 *10^-15 m, respectively. Assume that the charge is distributed uniformly throughout the volumes, that just before separation each fragment is at rest, and that fragments surfaces are in contact. The electric potential energy of two spherical fragments in MeV (1 MeV = 1.6 *10^-13 J) is

A charge q is moved a distance d in a uniform electric field E, as shown in the figure here. The displacement vector makes an angle $\alpha$ with the direction of the electric field. The work done on the charge is

The figure here shows a graph of the electric potential (independent of y and z) versus x in a certain region of space. The x component of the corresponding electric field at x = -2.0 cm is

A charge +q₁ is brought to a point a distance r from a charge +q. Then +q₁ is removed and a charge -q₁ is brought to the same point. If in the first case the electrostatic potential at r is V, the electrostatic potential at the same point in the second case is

Two concentric conducting spherical shells have radii r and R (> r) and charges q and Q, respectively. It can be shown that the electric potential difference between the two shells, V_R - V_r, is proportional to q(1/R - 1/r). If a thin conducting string connects the two shells, charge

The difference in electric potential between the accelerating plates in the electron gun of a TV tube is 25 kV, while the distance between them is 1.5 cm. The magnitude of the uniform electric field between the plates is

For an equipotential surface, all of the following are valid except

The figure here shows the equipotential lines in a certain region in the x-y plane. The electric field at point (1.0 cm, 4.0 cm) has

All of the following are legitimate units for electric field except

Two conducting spheres, A and B, are made of the same material and have radii r and 2r. The spheres are placed a distance d > 3r from each other. The first sphere has an initial charge Q, while the second is uncharged. The spheres are initially connected by a thin conducting wire; the wire is then removed. When electrostatic equilibrium has been reached, the magnitudes of the electric fields near the surfaces of the respective spheres are related by

Two conducting spheres are made of the same material and have radii r and 2r. The spheres are placed a distance d > 3r from each other and have initial charges of -2Q and 8Q, respectively. The spheres are initially connected by a thin conducting wire; the wire is then removed. The charges on the spheres after the removal of the wire are

As the distance from a negatively charged sheet of infinite dimensions and uniform charge density increases, the electric potential