Circuits Series and Parallel

Ohm’s Law In a very isolated situation, we know that: V = IR But how does this apply to the real world?

Circuits Ohm’s Law is the basis for how all circuits function. Examples of Circuits:

Circuits Ohm’s Law is the basis for how all circuits function. Examples of Circuits: Playstation

Circuits Ohm’s Law is the basis for how all circuits function. Examples of Circuits: Playstation Cell Phones

Circuits Ohm’s Law is the basis for how all circuits function. Examples of Circuits: Playstation Cell Phones Computers

Circuits Ohm’s Law is the basis for how all circuits function. Examples of Circuits: PlaystationAnything that gets Cell Phonesplugged into a wall Computersor a battery has a circuit

Making sense of circuits The best way to imagine a circuit is to think of traffic!

Electricity Terms Electrons Current ResistanceIf electricity is like Voltagetraffic, what would Wiresthe cars be??

Making sense of circuits Electricity comes from moving electrons. Cars are the electrons on the road. -q

Electricity Terms Electrons Current ResistanceCars drive on the Voltageroad. What Wiresrepresents the road?

Making sense of circuits Wires are the roads that electrons travel along.

Electricity Terms Electrons Current ResistanceThe gas in a car is Voltagethe Potential Energy Wiresthat makes it go. Which is the gas?

Making Sense of Circuits Voltage is like how much gas you have. It determines how far you can go and how long your car can run. V

Electricity Terms Electrons Current ResistanceThe cars are all Voltagedriving at one speed Wiresor another. What is speed representative of?

Making sense of circuits Current is the speed of the cars going down the road. I

Electricity Terms Electrons Current ResistanceIn traffic there’s Voltagealways construction Wiresthat slows the cars down.

Making sense of circuits Resistance is like roadwork on the road that slows traffic down. Remember: A resistor is anything that uses electricity. R

Electricity Terms Electrons Current Resistance Voltage Wires

Making sense of circuits Imagine these two trips around the block: Trip 1Trip 2

Making sense of circuits Which trip will result in slower traffic speeds? Trip 1Trip 2

Making sense of circuits If these were circuits instead of a road map, it would look like this: Trip 1Trip 2

Making sense of circuits Everything that applies to the traffic applies to the circuit. Trip 1 is faster, so current is higher too. Trip 1Trip 2

Making sense of circuits Which trip has the most amount of slow downs? Trip 1Trip 2

Making sense of circuits Which circuit has the most amount of resistance? Trip 1Trip 2

Series Circuits These kinds of circuit are called Series Circuits. Trip 1Trip 2

Series Circuits Series Circuits are like a one lane road. There’s only one way to go, so you have to go that way. If you run into construction, TOO BAD!!

Making sense of circuits Now let’s look at a more complicated road trip:

Making sense of circuits Which path will more cars take, A or B? Why? A B

Making sense of circuits Compare the current (car speed) and resistance (amount of construction) between A and B. A B

Making sense of circuits And the circuit would look like this: A B

Parallel Circuits These circuits are called Parallel Circuits. This is like a highway, where you can change lanes if one gets to slow.

Series vs. Parallel Circuits Let’s take a look at how different kinds of circuits will change things in the real world…

Traffic Report When we’re talking about traffic we want to know the overall delays, not what’s going on in each lane. (We don’t have all day!) We can describe a circuit by giving it’s overall resistance instead of listing each resistor as well…

Traffic Report If each construction zone takes 10 min to get through, what’s our total delay?

Traffic Report If each construction zone is a 10Ω light bulb, what is our overall resistance?

Traffic Report For Series Circuits, you have to go through all the delays, so we just add them up. R total = 10Ω +10Ω +10Ω= 30Ω

Traffic Report For Parallel Circuits, we have to handle things a little differently because there’s more than one way to go. Consider this circuit: A B

Traffic Report What is the total resistance if you take route A? (Each bulb is still 10Ω) A B

Traffic Report What is the total resistance if you take route A? (Each bulb is still 10Ω) A B 10Ω + 10Ω + 10Ω = 30Ω

Traffic Report What is the total resistance if you take route B? A B

Traffic Report What is the total resistance if you take route B? A B Just 10Ω.

Traffic Report Some electrons will take Route A, and some will take Route B. A B 30Ω 10Ω

Traffic Report To get our total resistance (the “Traffic Report”), we will add them together like this: A B 30Ω 10Ω

Traffic Report To get our total resistance (the “Traffic Report”), we will add them together like this:

Practice Find the total resistance for this circuit: Let each bulb have a resistance of 1Ω.

Practice Find the total resistance for this circuit:

Practice Find the total resistance for this circuit: Let each bulb have a resistance of 1Ω.

Practice Find the total resistance for this circuit: A=1Ω B=1Ω

Practice Find the total resistance for this circuit: A=1Ω B=1Ω