4. For an ideal electric quadruple, what is the relation between the electric field strength E and the distance r in the far field?
(A)
(B)
(C)
(D)

41. What can we infer from the passage? (A) Niagara Falls is not safe to visit. (B) The author thinks waterfalls are a spectacular form of natural beauty. (C) The best way to appreciate a waterfall is to read an encyclopedia. (D) The largest waterfall in the world lies in Asia.

1.Which of the following statements is not correct? (A)(B)(C)(D)

2.Which of the following statements is not correct? (A) A curl-less vector field can be expressed as the gradient of a scalar field. (B) A divergence-less vector field can be expressed as the curl of a vector feld. (C) A curl-lJess and divergence-less vector field is a constant vector field. (D) A smooth and rapidly decaying vector field can be expressed as the sum of a curl-less vector field and a divergence-less vector field.

3.A charged particle at rest is released in a region of uniform electric field in the y direction and uniform magnetic field in the z direction. Which of the following statements is not correct? (A) The motion of the particle in the y direction is periodic. (B) In average, the particle moves with a constant speed in the x direction. (C) The kinetic energy of the particle increases with time. (D) The magnetic field does no work on the particle.

5.Consider two long parallel wires of radius a, separated by a distance d. If d□ a, find the capacitance per unit length. (A)(B) (C) (D)

6. In the static case, consider an interface between the free space and a perfect conductor with some charges on the surface. Which of the following statements is not correct? (A) The electric field in the free space near the surface is proportional to the surface charge density. (B) There is no electric field in the conductor. (C) The surface charge would experience no electric force. (D) The electric potcntial is the same in the conductor, even near sharp edges.

7.An uncharged metal sphere is placed in an otherwise uniforn electric field . Find the induced surface charge density. (A) Zero everywhere on the sphere. (B) ε0E0cosθ (C) 2ε0E0cosθ (D) 3ε0E0cosθ

8.What does ρ in the Gauss's lawmean? (A) The free volume charge density. (B) The free surface charge density. (C) The sum of the polarization volume charge density and the free voiume charge density. (D) The sum of all surface charge density and volume charge density.

9.What does in the Ampcre's lawmean? (A) The free volume current density. (B) The free surface current density. (C) The sum of the polarization current density, the magnetization current density, and the free current density. (D) The sum of all surface current density and volume current density.

10. Consider a uniformly polarized dielectric sphere where the polarization inside the sphere is . Find the displacement ficld inside the sphere. (A)0 (B) (C)(D)