Figure 1.1. On the left is a battery labeled E1 which has its negative end connected to the bottom line of the circuit. The positive end of E1 connects to the left end of a resistor, R1. The right end of R1 connects to the top end of R2. The bottom end of R2 connects to the bottom line. The junction of R1 and R2 connects to the left end of R3. The right end of R3 connects to the top end of another battery labeled E2. The bottom end of E2 connects to the bottom line. On the left a semicircle and arrowhead indicates that I1 is flowing clockwise through E1, R1, and R2. Another semicircle and arrowhead indicates that I2 is flowing clockwise through R2, R3, and E2. Everything has polarity markings. The upper ends of both batteries are positive. The left ends of R1 and R3 are positive. R2 has two sets of polarity markings because there are two currents flowing through it. On the left I1 causes the upper end of R2 to be positive. On the right I2 causes the lower end of R2 to be positive. This seeming contradiction can exists because of the superposition theorem. End verbal description.
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