Series: Current is the same at all points. | Parallel: Total current is the sum of currents in each branch.

Series: Voltage drops add up to the battery voltage. | Parallel: Voltage is the same across each branch and equal to the battery's voltage.

Series: Adding resistors increases total resistance. | Parallel: Adding resistors decreases total resistance.

Series: $R_{total} = R_1 + R_2 + R_3 + ...$ | Parallel: $\frac{1}{R_{total}} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3} + ...$

Series: Current decreases. | Parallel: Total current from the source will decrease, but current through other branches remains relatively unchanged if the voltage source is ideal.

Series: Current is the same throughout. | Parallel: Current splits and recombines; total current is the sum of branch currents.

Series: Voltage drops add up to the battery voltage. | Parallel: Voltage is the same across each branch.

Series: Adding resistors increases total resistance. | Parallel: Adding resistors decreases total resistance.

Add the individual resistances: $R_{total} = R_1 + R_2 + R_3 + ...$

Calculate the reciprocal of the total resistance by summing the reciprocals of the individual resistances: $\frac{1}{R_{total}} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3} + ...$

1. Identify the junction. 2. Determine the currents entering the junction. 3. Determine the currents leaving the junction. 4. Apply the rule: ΣI_in = ΣI_out.