Exam 22: Electric Fields

The diagrams show four possible orientations of an electric dipole in a uniform electric field Rank them according to the magnitude of the torque exerted on the dipole by the field, least to greatest.

Positive charge +Q is uniformly distributed on the upper half of a rod and a negative charge -Q is uniformly distributed on the lower half. What is the direction of the electric field at point P, on the perpendicular bisector of the rod?

Two point particles, one with charge +8 *10^-9 C and the other with charge-2 *10^-9 C, are separated by 4 m. The electric field in N/C midway between them is:

Two point particles, with the same charge, are located at two vertices of an equilateral triangle. A third charged particle is placed so the electric field at the third vertex is zero. The third particle must:

Charge is placed on the surface of a 2.7-cm radius isolated conducting sphere. The surface charge density is uniform and has the value 6.9 *10^-6 C/m². The total charge on the sphere is:

The torque exerted by an electric field on a dipole is:

The dipole moment of a dipole in a 300-N/C electric field is initially perpendicular to the field, but it rotates so it is in the same direction as the field. If the moment has a magnitude of 2 * 10^-9 C . m the work done by the field is:

An electric field is most directly related to:

Two thin spherical shells, one with radius R and the other with radius 2R, surround an isolated charge point particle. The ratio of the number of field lines through the larger sphere to the number through the smaller is:

A uniform electric field of 300 N/C makes an angle of 25 $\degree$ with the dipole moment of an electric dipole. If the torque exerted by the field has a magnitude of 2.5 * 10^-7 N .m, the dipole moment must be:

The diagram shows the electric field lines in a region of space containing two small charged spheres (Y and Z). Then:

When the dipole moment of a dipole in a uniform electric field rotates to become more nearly aligned with the field:

The magnitude of the force of a 400-N/C electric field on a 0.02-C point charge is:

Two protons (p₁ and p₂) are on the x axis, as shown below. The directions of the electric field at points 1, 2, and 3 respectively, are:

An electron traveling north enters a region where the electric field is uniform and points west. The electron:

Two charged point particle are located at two vertices of an equilateral triangle and the electric field is zero at the third vertex. We conclude:

The diagram shows the electric field lines due to two charged parallel metal plates. We conclude that:

An electric dipole is oriented parallel to a uniform electric field, as shown. It is rotated to one of the five orientations shown below. Rank the final orientations according to the change in the potential energy of the dipole-field system, most negative to most positive.

An electric field exerts a torque on a dipole only if:

The diagram shows two identical particles, each with positive charge Q. The electric field at point P on the perpendicular bisector of the line joining them is: