Bài giảng Electromagnetic Fields – Prob - Chapter 2 - Trần Quang Việt
Electromagnetic Fields – Prob – ch_2
B = B0 [sin(ωt )ax − cos(ωt )ay ] (Wb / m2 )
D2.5. Given :
find the induced emf around each of the following close paths: (a) the
rectangular path from (0,0,0) to (0,1,0) to (0,1,1) to (0,0,1); (b) the
triangular path from (1,0,0) to (0,1,0) to (0,0,1) to (1,0,0); and (c) the
rectangular path from (0,0,0) to (1,1,0) to (1,1,1) to (0,0,1) to (0,0,0).
ωB
Ans :( a )−ωB0 cos(ωt ) (V );(b )−
0 cos(ωt −π / 4 ) (V )
2
( c )− 2ωB0 cos(ωt +π / 4) (V )
Trần Quang Việt – BMCS – Khoa Điện – ĐHBK Tp.HCM
Electromagnetic Fields – Prob – ch_2
2
E = E0te−t az
D2.8. For :
in free space, find the displacement
current crossing an area of 0.1m2 in the xy-plane from the –z-side to
the +z-side for each of the following value of t: (a) t=0;
(b )t =1/ 2 S;and (c) t=1 S
Ans :( a ) 0.1ε0E0 (A);(b ) 0 ( A);(c ) -0.1e-1ε0E0( A)
P2.18. A current density due to flow of charges is given by :
J = −( xax + yay + z2 az )A/ m2
Find the displacement current emanating from each of the following
close surfaces : (a) the surface of the cubical box bounded by the
plane x= 2, y= 2, and z= 2, and (b) the surface of the cyclindrical
box bounded by the surface r=1, z=0, and z=2
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Electromagnetic Fields – Prob – ch_2
P2.22. For each of the following charge distributions, find the
displacement flux emanating from the surface enclosing the charge :
2
( a )ρ( r,φ,z ) = ρ0e−r for r<1, 0<z<1 in cyclindrical coordinates;
and (b) ρ(r,θ,φ)=(ρ0/r)sin2θ for r<1, 0<θ <π /2 in spherical coordinates
BdS = 0
P2.23. Using the property that
, find the absolute value
of the magnetic flux crossing that portion of the surface y=sinx
ꢂ∫
S
B = B0( yax − xay ) Wb / m2
bounded by x=0, x=π, z=0 and z=1 for :
P2.29. Charge is distributed with uniform density ρ0 C/m3 in the
region a<r<2a in spherical coordinates. Find
plot Dr versus r.
everywhere and
D
Trần Quang Việt – BMCS – Khoa Điện – ĐHBK Tp.HCM
Electromagnetic Fields – Prob – ch_2
2
P2.28. Charge is distributed with uniform density ρ0e−r C / m3 in
the cyclindrical region r<1. Find everywhere.
D
P2.31. Current flows with density
A/m2 along an
J = J0( r / a )az
infinitely long solid cyclindrical wire of radius a having the z-axis
as its axis. Find everywhere and plot Hφ versus r.
H
P2.32. A coxial cable consits of an inner conductor of radius 3a and
an outer conductor of inner radius 4a and outer radius 5a. Assume
the cable to be infinitely long and its axis to be along the z-axis.
Current flows with uniform density in the +z-direction in the inner
conductor and returns with uniform density in the –z-direction in
the outer conductor. Find
everywhere and plot Hφ versus r
H
Trần Quang Việt – BMCS – Khoa Điện – ĐHBK Tp.HCM
2
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