chapter 23 circuits - university of maryland · · 2010-04-25... publishing as pearson...
TRANSCRIPT
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley.
• Circuits containing multiple elements
• Series and parallel combinations
• Electricity in the nervous system
Chapter 23 Circuits
Topics:
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Drawing Circuit Diagrams
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Checking Understanding
The following circuit has a battery, two capacitors and a resistor.
Which of the following circuit diagrams is the best representation of the above circuit?
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley.
The following circuit has a battery, two capacitors and a resistor.
Which of the following circuit diagrams is the best representation of the above circuit?
Answer
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Kirchhoff’s Laws
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Using Kirchhoff’s Laws
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The diagram below shows a segment of a circuit. What is the current in the 200 resistor? A. 0.5 A B. 1.0 A C. 1.5 A D. 2.0 A E. There is not enough information to decide.
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The diagram below shows a segment of a circuit. What is the current in the 200 resistor?
B. 1.0 A
Answer
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Series Resistors
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Parallel Resistors
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Electricity in the Nervous System
Understanding electrical signals in the nervous system.
The long fibers in the connecting the nerve cells in the picture are called axons, and they transmit electric signals between cells.
We start by discussing the latter (nerve cells)
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Model of a nerve cell
Cell membrane: separates regions of conducting fluid inside and outside the cell. Mainly two (positive) ions, potassium (K) and sodium (Na) move in and out.
Two mechanisms for this: - K-NA exchange - K-NA channels
This charge separation produces a potential difference between inside and outside of the cell and an electric field in the membrane.
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The cell’s resting potential
The electric potential is produced by a charge separation.
The membrane becomes polarized.
When there is no activity (rest) the potential difference is typically around 70mV (being smaller inside)
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Electricity in the Nervous System
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The propagation of nerve impulses
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Saltatory Conduction