Concept explainers
Repeat Problem 11.11, except the wave now propagates in fresh water, having conductivity a = 10-3 S/m, dielectric constant er' = 80.0, and permeability u0.
(a)
The loss tangent and whether the material is good dielectric or good conductor.
Answer to Problem 11.12P
The value of loss tangent is
Explanation of Solution
Calculation:
The line loss tangent is given by
Here,
The permeability
Here,
The conversion from
The conversion of
Hence, the frequency
The angular frequency
Here,
Substitute
Substitute
Substitute
Since the value of loss tangent is less than 1, the material is a good dielectric.
Conclusion:
The value of loss tangent is
(b)
The attenuation coefficient
Answer to Problem 11.12P
The attenuation coefficient
Explanation of Solution
Calculation:
For a good dielectric, the value of
The value of phase constant
Here,
The value of
Substitute the value of equations (2) and (4) in equation (3).
Substitute
The value of wave impedance for a medium is given by
Here,
Substitute
The impedance angle for a good dielectric is
The value of
Conclusion:
Therefore, the attenuation coefficient
(c)
The electric field in phasor form.
Answer to Problem 11.12P
The phasor expression of electric field is
Explanation of Solution
Calculation:
The electric field
Here,
Substitute
Conclusion:
The phasor expression of electric field is
(d)
The magnetic field in phasor form
Answer to Problem 11.12P
The magnetic field strength in phasor form is
Explanation of Solution
Calculation:
The magnetic field strength
Here,
Substitute
Conclusion:
Therefore, the magnetic field in phasor form is
(e)
The time averaging Poynting vector.
Answer to Problem 11.12P
The time averaging Poynting vector is
Explanation of Solution
Calculation:
The time averaging Poynting vector is given by
Here,
Substitute
Conclusion:
Therefore, the time averaging Poynting vector is
(f)
The 6-dB material thickness at which the wave power drops to 25 % of its value.
Answer to Problem 11.12P
There is no 6-dB material thickness.
Explanation of Solution
The attenuation constant
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Chapter 11 Solutions
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