In the circuit shown in Fig. the sources have emf's
ε1=1.5 V,ε2=2.0 V,ε3=2.5 V, and the resistances are equal to
R1=10Ω,R2=20Ω,R3=30Ω. The internal resistances of the sources are negligible. Find:
(a) the current flowing through the resistance
R1;
(b) a potential difference
φA−φB between the points
A and
B.