图1-4-20
A.Ea>Eb>Ec,φa>φb>φc B.Ea=Eb>Ec,φa=φb>φc
C.Ea=Eb=Ec,φa=φb>φc D.Ea>Ec>Eb,φa>φb>φc
D 画出导体空腔内外的电场线分布,Eb=0,但φb>0.