circuits series and parallel. ohm’s law in a very isolated situation, we know that: v = ir but how...
TRANSCRIPT
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:PlaystationCell Phones
Circuits
• Ohm’s Law is the basis for how all circuits function.
• Examples of Circuits:PlaystationCell PhonesComputers
Circuits
• Ohm’s Law is the basis for how all circuits function.
• Examples of Circuits:Playstation Anything that getsCell Phones plugged into a wallComputers or 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• Resistance If electricity is like• Voltage traffic, what would• Wires the cars be??
Making sense of circuits
• Electricity comes from moving electrons.• Cars are the electrons on the road.
-q
Electricity Terms
• Electrons• Current• Resistance Cars drive on the• Voltage road. What • Wires represents the
road?
Making sense of circuits
• Wires are the roads that electrons travel along.
Electricity Terms
• Electrons• Current• Resistance The gas in a car is• Voltage the Potential
Energy• Wires that 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• Resistance The cars are all• Voltage driving at one
speed• Wires or 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• Resistance In traffic there’s• Voltage always
construction• Wires that 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 1 Trip 2
Making sense of circuits
• Which trip will result in slower traffic speeds?
Trip 1 Trip 2
Making sense of circuits
• If these were circuits instead of a road map, it would look like this:
Trip 1 Trip 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 1 Trip 2
Making sense of circuits
• Which trip has the most amount of slow downs?
Trip 1 Trip 2
Making sense of circuits
• Which circuit has the most amount of resistance?
Trip 1 Trip 2
Series Circuits
• These kinds of circuit are called Series Circuits.
Trip 1 Trip 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.
• Rtotal = 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 B10Ω + 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 B30Ω 10Ω
Traffic Report
• To get our total resistance (the “Traffic Report”), we will add them together like this:
A B30Ω 10Ω
10
1
30
11
totalR
Traffic Report
• To get our total resistance (the “Traffic Report”), we will add them together like this:
total
total
total
total
R
R
R
R
5.7
))(13.0(1
13.01
10
1
30
11
Practice
• Find the total resistance for this circuit:
• Let each bulb have a resistance of 1Ω.
Practice
• Find the total resistance for this circuit:
41111
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=1Ωtotal
total
total
R
R
R
2
1
21
1
1
1
11