B I ngvab →V= ngab S U-U,=1B) RH= nq ng (1)R→n(2)9>0→R>0→U,>U2 q<0→R1<0→U1<U2 END = nqvabI nqab I v =⇒ ) bBI ( nq UU 1 21 =−⇒ nq R 1 H = )1( H → nR 0)2( H >→>→> UU0Rq 21 + v r F r S1 S2 Eq r B r a b I I END < → H < 00 → <UURq 21