13:2 : 4 (3) 4:3 S י VS Figure shows mixed grouping of identical cells each of e.m.f. 4 V and internal resistance 12. This combination can be replaced by an equivalent cell between A and B having e.m.f. E and internal resistance r, where HHHHHH (1) E = 72V r = 18 3) E=72V r = 2 A HHHHHHH HHHHHHH R www B (2) E = 24V r = 18 S = (4) E 24V r = 2 72 ไป 144 ​