Series and Parallel Circuits

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Series and Parallel Circuits
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Circuits

• Can either be series or parallel.

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Series

• Current only takes one path for electrons
• Current flows through every part of the circuit

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Lights in a Series
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Series

• If you add a resistor (like another light)
• Total resistance goes UP since all the current
  has must go through each resistor.

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Adding Resistors to Series

• Current in the circuit will go DOWN (lights will
  dim)
• If you remove a light bulb or one burns outall
  go out!

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Current in Series

• Current is the same at all points
• Use Ohms Law to find current using resistance
  and voltage

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Calculating Current Example
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Voltage in Series

• Voltage is reduced by each resistance voltage
  drop

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Calculating Voltage Example
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Resistance in Series

• Add up all resistors to get total
• Total resistance will go up because all of the
  current must go through each resistor.

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Calculating Resistance Example
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Sample Problem 1

• Draw a series circuit with two 1.5 V batteries, 3
  resistors, and a current of 0.5 A.
• What is the total voltage of the circuit?
• What is the resistance of each resistor?
• What is the voltage drop across each resistor?
  Label on your circuit.

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Parallel Circuits

• Has at least one point where current divides
• More than one path for current to flow
• Paths are also known as branches

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Lights in Parallel
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Parallel

• If you add a resistor
• Total resistance goes down
• Total current goes up when you add another path

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Removing a Light Bulb

• If you remove a light bulb or one burns out, the
  others stay on because the circuit is still
  closed.

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Current in Parallel

• Current flows into a branching point, the same
  total current must flow out again
• Current depends on resistance in each branch

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Calculating Current Example
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Voltage in Parallel

• Voltage is the same across each branch because
  each branch is on the same wire

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Calculating Voltage Example
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Resistance in Parallel

• Calculate current in each branch based on
  resistance in each branch by using Ohms Law

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Calculating Resistance Example
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Practice problem 2

• Draw a parallel circuit with two resistors (one
  on each branch) and a 12 V battery.
• What is the voltage through each resistor?
• What is the current flowing through each branch?

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Toll RoadCircuit Analogy
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Toll Booth Explanation

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

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Batteries in Series and Parallel
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• In seriesThe voltage is increased.
• In parallelNo change in voltage these batteries
  will last longer!

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One More FINAL Thing

• Two Types of Current
• DCDirect Currentproduced by solar cells and
  chemical cells (batteries)
• Current only flows in one direction.

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2nd type of current

• ACAlternating Current
• Current flows back and forth (alternates)
• Found in homes
• Generators produce AC current