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