Draw a diagram of a dipole at height h above a flat ground plane,and orientated at angle α with the ground plane. Set the origin of yourvector space to be the point on the ground directly beneath the centre of thedipole, and use the method of images to find an expression for the E-field ofthe dipole with the ground plane.To simplify this problem, you may assume you know the angles, θ, in theexpression for the dipole field for both the dipole and its image.1
Question
Draw a diagram of a dipole at height h above a flat ground plane,and orientated at angle α with the ground plane. Set the origin of yourvector space to be the point on the ground directly beneath the centre of thedipole, and use the method of images to find an expression for the E-field ofthe dipole with the ground plane.To simplify this problem, you may assume you know the angles, θ, in theexpression for the dipole field for both the dipole and its image.1
Solution
I'm sorry, but as a text-based AI, I'm unable to draw diagrams. However, I can guide you through the process of how to draw it and find the expression for the E-field of the dipole with the ground plane.
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Start by drawing a flat horizontal line to represent the ground plane. Mark a point on this line to represent the origin of your vector space.
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Draw a vertical line from the origin to represent the height, h, above the ground plane. This line ends at the center of the dipole.
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Draw the dipole at the top of this line. A dipole is simply two charges of equal magnitude but opposite sign separated by a distance. Represent these charges as two dots, one positive (usually denoted by a plus sign) and one negative (denoted by a minus sign).
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The dipole is oriented at an angle α with the ground plane. Show this by drawing a line from the center of the dipole that forms an angle α with the ground plane.
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The method of images involves replacing the ground plane with an imaginary plane that has the same effect on the dipole. Draw this imaginary plane beneath the ground plane. The image of the dipole in this plane is an identical dipole but with the charges reversed, and it's located at the same height h below the ground plane.
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Now, to find an expression for the E-field of the dipole with the ground plane, you can use the formula for the electric field of a dipole:
E = k * (2p cos θ/r^3 - p sin θ/r^2)
where k is Coulomb's constant, p is the dipole moment, r is the distance from the dipole, and θ is the angle.
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Since you have both the dipole and its image, you need to add the contributions from both to get the total E-field. Remember that the image dipole has the charges reversed, so its contribution will be subtracted.
E_total = E_dipole - E_image
I hope this helps! Let me know if you have any other questions.
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Time left 0:01:01Question 11Not yet answeredMarked out of 15.00Flag questionTipsQuestion textThe electric and magnetic fields of a short dipole (length L << λ) that is placed at the origin and oriented parallel to the z axis of the standard spherical coordinate system can be calculated in the general case at the point r,θ,φ from the following formulaeE⃗ =Erur+Eθuθ𝐸→=𝐸𝑟𝑢𝑟+𝐸𝜃𝑢𝜃 whereEr=j2ωμILcosθe−jkr4πr(1jkr+1(jkr)2)𝐸𝑟=𝑗2𝜔𝜇𝐼𝐿cos𝜃𝑒−𝑗𝑘𝑟4𝜋𝑟(1𝑗𝑘𝑟+1(𝑗𝑘𝑟)2)Eθ=jωμILsinθe−jkr4πr(1+1jkr+1(jkr)2)𝐸𝜃=𝑗𝜔𝜇𝐼𝐿sin𝜃𝑒−𝑗𝑘𝑟4𝜋𝑟(1+1𝑗𝑘𝑟+1(𝑗𝑘𝑟)2) andH⃗ =Hϕuϕ=uϕjkLIsinθe−jkr4πr(1+1jkr)𝐻→=𝐻𝜙𝑢𝜙=𝑢𝜙𝑗𝑘𝐿𝐼sin𝜃𝑒−𝑗𝑘𝑟4𝜋𝑟(1+1𝑗𝑘𝑟)ω is the angular frequency, I is the amplitude of the electric current in the dipole, L is the length of the dipole, and k = 2π/λ is the wave number.(a) Simplify the expression for the wave impedance of a short dipole η=|E⃗ |/|H⃗ |𝜂=|𝐸→|/|𝐻→| as much as possible when θ = 90°. (Keep in mind part b)(b) Using the software of your choice, plot the wave impedance η as a function of the distance-to-wavelength ratio r/λ along the axis perpendicular to the antenna (θ = 90°). Choose, e.g., 0.05≤r/λ≤3 and 0 Ω≤η≤1000 Ω.(c) Mark on the plot i) the level where η = η0 =377 Ω, ii) the distance r/λ = 1/(2π), and iii) the distance r/λ at which η = 0.997η0.(d) What is the reactance of a short dipole like? Which field (E or H) dominates in the distance range r/λ = 1/(2π)? How is this related to the reactance of a short dipole?(e) What distance can be considered as the outer boundary of the reactive near fields of a short dipole?(f) What is the distance of the far field region of a short dipole?(g) How would you assume that the wave impedance curve changes for a small loop antenna? What is the reactance of a small loop, inductive or capacitive?
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