**Series and Parallel Circuits**

Series Circuits

Properties of a Series Circuit

Parallel Circuits

Resistive Elements (resistors) are connected between two points (called nodes)

Properties of Parallel Circuits

Resistive Elements (resistors) are connected end-to-end in one line

One Path for electrons to flow

CURRENT

Properties of a Series Circuit

VOLTAGE

Properties of a Series Circuit

RESISTANCE

CURRENT

Properties of Parallel Circuits

VOLTAGE

Properties of Parallel Circuits

RESISTANCE

Many paths (at least two) for electrons to flow

Current follows in a single path

Current is the same in each resistor

The total potential difference, V, at the terminals must equal the sum of the separate potential differences across each resistors.

Each resistor only gets a portion of the total voltage.

The total resistance is the sum of each individual resistor.

The total resistance is greater then the largest resistor.

Current has more than one path.

Current is divided among resistors.

The sum of the current in each branch is equal to the total.

The same potential difference exists across each resistor.

Each resistor gets the same voltage

The total resistance is less than the smallest resistor

Draw another example...

Draw another example...

**Electrical Meters**

**Ammeters**

Measure ______________

- Have ______ resistance, like a bare wire. Can cause a short circuit!

- To connect: break the circuit where you want to measure current and insert the ammeter.

- Do NOT split the path of the electrons and make a new way for current to flow.

DRAW IT!

**Electrical Meters**

**Voltmeters**

Measure ________________

- Have _______ resistance, act like a big resistor (can almost stop current)

- To connect: place one lead (wire) on each side of the potential difference you wish to measure.

- Do NOT break your original complete circuit.

DRAW IT!

Whats the total resistance (equivalent resistance) of a circuit with a 3 ohm, 4 ohm, and 5 ohm resistor connected in parallel, in which 7.05 amps flow from the 9V battery?

The TOTAL resistance is called the...

Equivalent Resistance

**Solving Problems involving Series & Parallel Circuits**

**Rules:**

**1. Identify circuit elements in Series and/or parallel**

If series, I is the same everywhere

If parallel, V is the same everywhere

2. Find Req if you can for those elements

3. Use V=IR (I=V/R or R=V/I) where you can

If series, I is the same everywhere

If parallel, V is the same everywhere

2. Find Req if you can for those elements

3. Use V=IR (I=V/R or R=V/I) where you can

**P= VI**