16.6 Parallel and Series Circuits. Possible Paths We are now going to look at the different paths...
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Transcript of 16.6 Parallel and Series Circuits. Possible Paths We are now going to look at the different paths...
![Page 1: 16.6 Parallel and Series Circuits. Possible Paths We are now going to look at the different paths that you can set up for electrons Depending on the path.](https://reader035.fdocuments.us/reader035/viewer/2022081515/5697c0111a28abf838ccbcb0/html5/thumbnails/1.jpg)
16.6 Parallel and Series Circuits
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Possible Paths
• We are now going to look at the different paths that you can set up for electrons
• Depending on the path you provide, you can control the work that electrons do for you
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Tracing electrons
• To better understand circuits, there is one simple way to figure how they will travel – which will determine how the circuit works
• ELECTRONS TAKE THE SHORTEST PATH TOWARDS THE END OF THE CIRCUIT
• ELECTRONS NEVER BACKTRACK
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Imagine 2 electrons that are leaving the battery at the same timeWhen they reach the junction they each have a choice: they can move forward or make a turnAt the next junction – the blue electron MUST make a RIGHT turn – this will take it directly towards the POSITIVE POLE of the battery. Likewise, the red electron will continue forward – if it was to turn right, it would move back towards the NEGATIVE POLE of the battery
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Series and Parallel Circuits
• There are 2 basic types of circuits • SERIES: there is only one possible
path for the electrons to travel• PARALLEL: there are 2 or more
possible paths for electrons to travel
• This fact gives different properties to series and parallel circuits
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Series and Parallel circuits are like roads
SERIES
PARALLEL
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Notice:
• Series circuits provide a single path
• Parallel circuits provide multiple paths
• The number of cars that take a path depend on how easy it is to take the path (bigger the road, less traffic)
• Same with electrons – more electrons will take the path with least resistance – so current increases in those paths
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Naming loads in circuits
R1
R2
•Resistors are numbered
•Therefore:
•The voltage for R1 is referred to as V1
•The current for R1 is referred to as I1
•RT is the total resistance of the circuit
RT
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Sample problem
• Which of the following resistors are parallel to each other, and which are in series?
R1
R2
R3
PARALLEL TO R3
R2 and R3 ARE IN SERIES
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Keeping track of V, I, R
• In all circuits, you are always asking yourself what the V, I, and R is of each load in the circuit
• In order to calculate this, you must understand the basic rules associated with each type of circuit
• They were developed by a Russian scientist named Kirchoff and therefore are known as KIRCHOFF’S LAWS (KL)
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KL for voltage in Series Circuits
• Because electrons MUST travel through each load in the circuit, they have to give up energy to each one as they do so
• That means the total energy that an electron gives up at each load is equal to what it started with at the start
• VT = V1 + V2 + V3 + …+Vn
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Sample question
• In a series circuit, one resistor has a voltage of 3 V and another has a voltage of 2 V. What is the total voltage provided by the battery?
V1
V2
VT
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KL for current in a series circuit
• Since a series circuit provides no other pathway – the current stays constant at all points
• It is like a single water pipe that has no back up – the flow of water is the same at the start as it is in the middle and the end – since water from the back pushes water at the front
• IT = I1 = I2 = I3 = … = I4
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Sample problem
• The current leaving a battery that is connected to a series circuit is measured as being 5 A. What is the current moving through the two resistors in the circuit?
I1
I2
IT
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KL for voltage in parallel circuits
• In a parallel circuit, electrons only have to move through the loads that are in their paths
• That means that each electron only has to give up energy to the load in their path
• Each electron gives up the same amount of energy
• So the voltage of resistors parallel to each other are equal to each other
• VT = V1 = V2 = V3 = … = Vn
I1
I2
IT
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Sample problem
• Two parallel resistors are attached to a battery providing 9 V of power. What is the voltage across the two resistors?
VT
V1
V2
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KL law for current in parallel circuits
• In parallel circuits, electrons split up
• That means the current splits up
• If you add up the current in each path, you will have the total current of the circuit
• IT = I1 + I2 + I3 + … + In
IT
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Sample problem
• A parallel circuit has 2 resistors. If the total current leaving the battery is 10 A, and the first resistor has a current of 2 A, what is the current in the second resistor?
IT
I1
I2
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Kirchoff’s Laws for Resistance
• Using Ohm’s Law and KL for voltage and current in parallel and series circuits, the resistance of each type of circuit can also be analyzed as well
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KL for Resistance in Series Circuits• In a Series circuit, since:
• VT = V1 + V2 + V3 + …+Vn
• And V = IR• Then:• IRT = IR1 + IR2 + IR3 + …+IRn
• Therefore: since the I values are the same, they cancel out on both sides giving:
• RT = R1 + R2 + R3 + …+Rn
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KL for Resistance in Parallel Circuits• In a parallel circuit, since:• IT = I1 + I2 + I3 + … + In• And I = V/R, therefore:• V/RT = V/R1 + V/R2 + V/R3 + .. +
V/Rn
• Since the voltage value is the same in a parallel circuit, the V’s cancel out on the RS and LS giving:
• 1/RT = 1/R1 + 1/R2 + 1/R3 + .. + 1/Rn