CircuitsCan either be series or parallel.

SeriesCurrent only takes one path for electrons

Current flows through every part of the circuit

Lights in a Series

SeriesIf 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 SeriesCurrent is the same at all points

Use Ohm’s Law to find current using resistance and voltage

Calculating Current Example:

Voltage in SeriesVoltage is reduced by each resistance – voltage drop

Calculating Voltage Example

Resistance in SeriesAdd up all resistors to get totalTotal resistance will go up because all of the current must go through each resistor.

Calculating Resistance Example:

Sample Problem #1 Draw a series circuit with two 1.5 V batteries, 3 resistors, and a current of 0.5 A.

1. What is the total voltage of the circuit?

2. What is the resistance of each resistor?

3. What is the voltage drop across each resistor? Label on your circuit.

Parallel CircuitsHas at least one point where current divides

More than one path for current to flow

Paths are also known as branches

Lights in Parallel

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

Calculating Current Example:

Voltage in ParallelVoltage is the same across each branch – because each branch is on the same wire

Calculating Voltage Example:

Resistance in Parallel

Calculate current in each branch based on resistance in each branch by using Ohm’s Law

Calculating Resistance Example:

Practice problem #2Draw a parallel circuit with

two resistors (one on each branch) and a 12 V battery.

1. What is the voltage through each resistor?

2. What is the current flowing through each branch?

Toll Road—Circuit Analogy

Toll Booth ExplanationAdding toll booths in series increases resistance and slows the current flow.

Adding toll booths in parallel lowers resistance and increases the current flow.

Batteries in Series and Parallel:

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 CurrentCurrent flows back and forth (alternates)

Found in homesGenerators produce AC current