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## Series and Parallel Circuits

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**Circuits**• Can either be series or parallel.**Series**• Current only takes one path for electrons • Current flows through every part of the circuit**Series**• If you add a resistor (like another light): • Total resistance goes UP since all the current has must go through each resistor.**Adding Resistors to Series:**• Current in the circuit will go DOWN (lights will dim) • If you remove a light bulb or one burns out—all go out!**Current in Series**• Current is the same at all points • Use Ohm’s Law to find current using resistance and voltage**Voltage in Series**• Voltage is reduced by each resistance – voltage drop**Resistance in Series**• Add up all resistors to get total • Total resistance will go up because all of the current must go through each resistor.**Sample Problem #1**• Draw a series circuit with two 1.5 V batteries, 3 resistors, and a current of 0.5 A. • What is the total voltage of the circuit? • What is the resistance of each resistor? • What is the voltage drop across each resistor? Label on your circuit.**Parallel Circuits**• Has at least one point where current divides • More than one path for current to flow • Paths are also known as branches**Parallel:**• If you add a resistor: • Total resistance goes down • Total current goes up when you add another path**Removing a Light Bulb**• If you remove a light bulb or one burns out, the others stay on because the circuit is still closed.**Current in Parallel**• Current flows into a branching point, the same total current must flow out again • Current depends on resistance in each branch**Voltage in Parallel**• Voltage is the same across each branch – because each branch is on the same wire**Resistance in Parallel**• Calculate current in each branch based on resistance in each branch by using Ohm’s Law**Practice problem #2**• Draw a parallel circuit with two resistors (one on each branch) and a 12 V battery. • What is the voltage through each resistor? • What is the current flowing through each branch?**Toll Booth Explanation**• Adding toll booths in series increases resistance and slows the current flow. • Adding toll booths in parallel lowers resistance and increases the current flow.**In series—The voltage is increased.**• In parallel—No change in voltage; these batteries will last longer!**One More FINAL Thing:**• Two Types of Current: • DC—Direct Current—produced by solar cells and chemical cells (batteries) • Current only flows in one direction.**2nd type of current:**• AC—Alternating Current • Current flows back and forth (alternates) • Found in homes • Generators produce AC current