Bài giảng Electromagnetic Fields - Chapter 4 - Trần Quang Việt

Nội dung text: Bài giảng Electromagnetic Fields - Chapter 4 - Trần Quang Việt

1. Electromagnetic Fields – Prob – ch_4 D4.7. Compute the propagation constant and instrinsic inpendance -5 5 for the following cases: (a) σ = 10 S/m, ε=5 ε0, µ=µ0, and f=10 Hz; 9 (b) σ = 4S/m, ε=80 ε0, µ=µ0, and f=10 Hz Ans :(a ) (0.0083+j0.00476) (m-1 ), 163.54∠ 9.9 0 (Ω ) ; (b) (. 77 84+ j 202 .)(m),. 86−1 36 34 ∠ 20 . 99 0 ()Ω D4.8. For a uniform plane wave of frequency 10 6Hz propagating in a nonmagnetic ( µ=µ0) material medium, the propagation constant is known to be (0.05+j0.1) m -1. Find the following: (a) the distance in which the fields are attenuated by e -1; (b) the distance in which the fields undergo a change of phase by 1 rad; (c) the distance that a constant phase of the wave travels in 1 µs; (d) the ratio of the amplitudes of the electric and magnetic fields; and (e) the phase difference between the electric and magnetic fields. Ans :(a ) 20m; (b) 10m; (c) 62.83m; (d) 70.62Ω ; (e ) 0.1476 π  Tr ần Quang Vi ệt – BMCS – Khoa Điện – ĐHBK Tp.HCM Electromagnetic Fields – Prob – ch_4 D4.9. The magnetic field associated with a uniform plane wave propagating in the +z-direction in a nonmagnetic ( µ=µ0) material medium is given by:
   
     − z 7 H= He0 cos(6π . 10 t − 3 z)a(A/m)y Find the following : (a) the instantaneous power flow across a surface of area 1m 2 in the z=0 plane at t=0; (b) the time-average power flow across a surface of area 1m 2 in z=0 plane; and (c) the time-average power flow across a surface of area 1m 2 in the z=1 plane 2 2 2 Ans :(a ) 102.57H0 (W); (b) 51.28H 0 (W); (c) 6.94H 0 (W )  Tr ần Quang Vi ệt – BMCS – Khoa Điện – ĐHBK Tp.HCM 1