Figure 1. A series circuit, starting at the lower left corner a battery goes up with the positive side at the top. A resistor labeled R1 goes from the top of the battery to the right. The other end of the resistor connects to a second resistor labeled R2 which continues to the right. A third resistor connects to the right end of R2. The right end of the third resistor labeled R3 connects to the top, positive end, of a battery which goes down. The negative side of the battery on the right connects to the negative side of the battery on the left, completing the circuit. The battery on the left is labeled E1 = 15 volts. The battery on the right is labeled E2 = 10 volts.
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