110年 - [非官方正解]110 國立清華大學碩士班考試入學試題_聯合招生:電磁學#105337

1. A static charge distribution produces a radial electrical field

where A and b are constants. Which are possible total charges Q?
(A) 4TE₀A
(B) 2TE₀A
(C) 0
(D) -2TE₀A
(E) -4TTE₀A

2. If Pis the polarization vector and E is the electric field, then in the equation = , a in general are (A) Scalar (B) Vector (C) Tensor (D) Number (E) Matrix

4. Suppose a point charge q is held a distance d above an infinite grounded conducting plane. Given that the conducting plane is the x-y plane and the point charge q is at (0, 0, d). (A) The potential on the conducting plane is constant. (B) The potential far away from the charge is 0. (C) An image charge q can be set at (0, 0, -d) to remove the conducting plane while still satisfying the same boundary conditions. (D) The induced charge on the conducting plane is O (E) The induced charge on the conducting plane is

5. An uncharged metal sphere of radius R is placed in an otherwise uniform electric filed . The field will push positive charge to the northern (i.e., z＞ 0) surface of the sphere, leaving a negative charge on the southern surface. (A) The potential at r→∞ is 0. (B) The potential when r ＞＞ R (the radius of the sphere) is -E₀rcosθ. (C) The potential inside the sphere is E₀rcosθ. (D) The potential on the surface of the sphere is E₀Rcosθ. (E) The induced charge density is -3E₀E₀cosθ.

6. Given that dipole moment and polarization . (A) (B)(C) (D) (E)

7. Which are correct with the Poynting vector ? (A) is the energy per unit area and per unit time, transported by the electromagnetic fields. (B) is the electromagnetic force per unit area acting on a surface. (C) /c² is the momentum current density transported by the fields. (D) /c² is the momentum per unit volume stored in the electromagnetic fields. (E) /c² is the work done on the charges by the electromagnetic force.

8. Assume the wave guide is a perfect conductor, so that the boundary conditions
ㆍ Given the general form
determine which expressions are true?
(A)
(B)
(C)
(D)

(E)

9. A spherical shell of radius R, carrying a uniform surface charge o, is set spinning
at angular velocity .
(A) The vector potential for r≤R
(B) The vector potential for r≤R
(C) The vector potential for r≤R
(D) The magnetic field for r≤R
(E) The magnetic field for r≤R

10. Suppose a normal incidence occurred between tow linear media (n₁ →＞ n₂)
(A) The reflection coefficient
(B) The reflection coefficient
(C) The reflection coefficient
(D) The transmission coefficient
(E) The transmission coefficient