Electricity and Magnetism Answers

There is an electric field at point P, A very small charge isplaced at this point and experiences a force. Another very small charge is then placed at this point and experiences a force that differs in both magnitude and direction from that experienced by the first charge. How can these two different forces result from the single electric charge that exsists at point P?

The uniform fields shown in Figure 5.18 are near a dielectric–dielectric boundary but on opposite sides of it. Which configurations are correct? Assume that the boundary is charge free and that epsilon 2 > epsilon 1.

The relaxation time of mica (sigma = 10^-15 S/m, epsilon r = 6) is

(a) 5 x 10^-10 s

(b) 10^-6 s

(c) 5 hr

(d) 10 hr

(e) 15 hr

The formula R = l / (sigma S) is for thin wires.

(a) True

(b) False

(c) Not necessarily

Seawater has epsilon r = 80. Its permittivity is

(a) 81

(b) 79

(c) 5.162 x 10^-10 F/m

(d) 7.074 x 10^-10 F/m

Both epsilon 0 and Xe are dimensionless.

(a) True

(b) False

If = nabla . D = epsilon nabla . E and nabla . J = sigma nabla . E in a given material, the material is said to be

(a) Linear

(b) Homogeneous

(c) Isotropic

(d) Linear and homogeneous

(e) Linear and isotropic

(f) Isotropic and homogeneous

The electric conditions (charge and potential) inside and outside an electric screening are completely independent of one another.

(a) True

(b) False

Which of the following statements are incorrect?

(a) The conductivities of conductors and insulators vary with temperature and frequency. (b) A conductor is an equipotential body in steady state, and E is always tangential to the conductor.

(c) Nonpolar molecules have no permanent dipoles.

(d) In a linear dielectric, P varies linearly with E.