Question 1.
(a) Define voltage. Specifically, what does it mean to say that the voltage between two points is +25 volts?
(b) An electric scalar potential V is given by V(x, y, z) = -3x2yz. Calculate the electric field from this potential. Show that this electric field is conservative. Show Work!
Question 2. A charge of Q1 =10-3 Coulombs is located at (2, 0) and a charge of Q2 = 2 x 10-3 Coulombs is located at (-4,0). (Note: Co = 8.854 x 10-12 F/m.)
(a) Including units, what is the total electric energy in the field of these two charges?
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(b) Including units, calculate the potential at point (0,0). How much work (in joules) is required to bring a charge of Q = 10-3 Coulombs from oo to point(0, 0)? Assume the potential V(∞) = 0.
Question 3.
(a) Calculate the potential at point P located a distance z above the center of a charged disk of radius a and surface charge density p. Coulombs per square meter. Please show all work. An integral that you may need is
∫ΡdΡ/(√(Ρ2 + z2)) = √(Ρ2 + z2)
The elemental area in cylindrical coordinates is dA = ΡdΡdΦm2.
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(b) Calculate the electric field at P. Use back of page if necessary.
Question 4. A charge +Q is located at the center of a shell of dielectric (inner radius r1 and outer radius r2) with a dielectric constant ∈r. Inside and outside of the shell is free space. Plot the electric field E→, the electric flux density D→, and the polarization P in the three regions 0 < r < r1,r1 < r < r2 and r > r2.
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Question 5. A parallel place capacitor has an equivalent plate area of A = 2 m2 and is charged to 20 volts. The dielectric has a permittivity of er = 12 and a plate separation of d = 0.0002 m. Include units in all answers. (Note: eo = 8.854 x 10-12 F/m.)
(a) Calculate the capacitance C.
(b) Calculate the total charge Q stored on the capacitor.
(c) Calculate the surface charge density on the plates, Ρs.
(d) Calculate the electric field E between the plates of the capacitor.
(e) From E, calculate the electric displacement D in the dielectric.
(f) Calculate the electric susceptibility xE of the dielectric.
(g) Calculate the electric polarization P in the dielectric.
(h) Calculate the total energy stored in the capacitor.
(i) Briefly and dearly explain the physical significance of the dielectric constant ∈r. For example, what is the difference between a material with a dielectric constant ∈r = 12 and a material with dielectric constant ∈r = 5?