Engineering, 07.06.2021 15:40 Catracho3619
Electromagnetic waves propagate much differently in conductors than they do in dielectrics or in vacuum. If the resistivity of the conductor is sufficiently low (that is, if it is a sufficiently good conductor), the oscillating electric field of the wave gives rise to an oscillating conduction current that is much larger than the disp1acement current. In this case, the wave equation for an electric field E(x, t) = E,(x, t)J propagating in the +x-direction within a conductor is where µ is the permeability of the conductor and p is its resistivity.
(a) A solution to this wave equation is where kc = √wµ/2p. Verify this by substituting E, (x, t) into the above wave equation.
(b) The exponential term shows that the electric field decreases in amplitude as it propagates. Explain why this happens.
(c) Show that the electric field amplitude decreases by a factor of 1/e in a distance 1/kc = √2plwµ, and calculate this distance for a radio wave with frequency f = 1.0 MHz in copper (resistivity 1.72 x 10-8 Ω ∙ m; permeability µ = µ0). Since this distance is so short, electromagnetic waves of this frequency can hardly propagate at all into copper. Instead, they are reflected at the surface of the metal. This is why radio waves cannot penetrate through copper or other metals, and why radio reception is poor inside a metal structure.
Answers: 2
Engineering, 04.07.2019 18:10
Afluid flows with a velocity field given by v=(x/t)i.. determine the local and convective accelerations when x=3 and t=1.
Answers: 2
Engineering, 04.07.2019 18:10
The higher the astm grain-size number, the coarser the grain is. a)-true b)-false
Answers: 3
Engineering, 04.07.2019 18:20
Acertain flow of air (at stp) has a velocity distribution given by v i (in ft/s). if this flow is going through a 4 ft square area in the yz-plane (centered at the origin), what is the mass flow rate (in lbm/s)?
Answers: 2
Engineering, 04.07.2019 18:20
Apiston-cylinder device contains 0.1 m3 of liquid water and 0.9 m3 of water vapor in equilibrium at 800 kpa. heat is transferred at constant pressure until the temperature of water reaches 350 °c. determine (a) the quality of water at the initial state (b) the work associated with this process, (c) the heat associated with this process.
Answers: 2
Electromagnetic waves propagate much differently in conductors than they do in dielectrics or in vac...
English, 09.12.2021 16:40
SAT, 09.12.2021 16:40
English, 09.12.2021 16:40
Arts, 09.12.2021 16:40
Mathematics, 09.12.2021 16:40