Download Section 6: Current, Voltage, and Resistance in Parallel and Series

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Section 6: Current, Voltage, and
Resistance in Parallel and Series Circuits
Lesson 3
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Physics Talk – Series and Parallel Circuit Problems
o Do sample problems 1 and 2 on pages 650-654.
o Emphasize that Ohm’s Law applies to each resistor and that once you have
used VT = ITRT for the entire circuit, you can use Ohm’s law for each
resistor separately V1 = I1R1 and V2 = I2R2 and V3 = I3R3
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(10 minutes for each problem = 20 minutes)
Deriving the equation to calculate total resistance in series and parallel circuits – -Optionalo If you choose to show how the formulas for resistance are derived, you
can assign some of the problems on page 656 for HW.
What do you think now?
o Revisit the two questions from the beginning of the section and have your
students answer them in their log.
o (4 minutes)
Essential Questions – Students should answer these questions in their log.
o What does it mean?
 Explain how the voltage of each light bulb in a parallel circuit can
be equal to the voltage of the power source.
o How do you know?
 Do you have any evidence that that is true?
o Why do you believe?
 Kirchoff’s Second Law = conservation of energy. How can the
voltage relationship of each resistor compare to the voltage of the
battery?
o Why should you care?
 Remind your students that every circuit in their home is a parallel
circuit. Their bedroom is one circuit, the living room might be
another circuit and the kitchen probably has several circuits, each
of which has a maximum of 15 or 20 amps. If you turn off the
toaster, the microwave still works which means it is a parallel
circuit. How will your knowledge of circuits, both parallel and
series, be put to use in your training manual?
o (10 minutes)
Reflecting on the Chapter Challenge
o Give each chapter Challenge team time to discuss the issue of how to
solve the problem of not exceeding the maximum 2400 W at any one time.
o Draw a picture of a home and draw several different circuits. Each circuit
is a parallel circuit as discussed above.
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HW
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Physics to Go
Page 658 & 659 #8, 10, 11, 12, 13, 16, 17, 18
Next Day
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HW
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Students may have had difficulty with the HW so work out problems 10
(series) and 13 (parallel) on the board. Then suggest if they had trouble
with any that they try them again for tomorrow tonight.
(10 minutes)