(B) dfrac (9)(4pi {varepsilon )_(0)a}-|||-(C) -dfrac (9)(8pi {varepsilon )_(0)a}
U=0 (B) E=0 , =dfrac (9)(2pi {varepsilon )_(0)a} q q-|||-(C) =dfrac (q)(2pi {var
U=0-|||-(B) E=0 . =dfrac (q)(2pi {varepsilon )_(0)a}-|||-(C) =dfrac (q)(2pi {var
dfrac (30)(2{varepsilon )_(0)}-|||-C. dfrac (sigma )({varepsilon )_(0)}-|||-D. d
(B) dfrac (lambda )(2pi {varepsilon )_(0)a}. (C) dfrac (lambda )(4pi {varepsilon
(B) dfrac (9)(2pi {c)_(0)(y)^2} - y↑-|||-(0,y)-|||-+q-|||-(C) dfrac (qa)(2pi {va
(B) dfrac (9)(2pi {c)_(0)(y)^2} - y 个-|||-P(0,y)-|||-+q-|||-(C) dfrac (qa)(2pi {
dfrac (qQ)(4pi {varepsilon )_(0)(d)_(1)} B. dfrac (qQ)(2pi {varepsilon )_(0)(d)_
dfrac (qQ)(4pi {varepsilon )_(0)l} C. dfrac (qQ)(2pi {varepsilon )_(0)l} D. -dfr
=dfrac (Q)(4pi {varepsilon )_(0)r}-|||-(D) =dfrac (Q)(4pi {varepsilon )_(0)(r)^2