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Chapter 21: Q15CQ (page 772)
Given a battery, an assortment of resistors, and a variety of voltage and current measuring devices, describe how you would determine the internal resistance of the battery.
Internal resistance is
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Would your headlights dim when you start your car’s engine if the wires in your automobile were superconductors? (Do not neglect the battery’s internal resistance.) Explain.
A person with body resistance between his hands ofaccidentally grasps the terminals ofa power supply. (Do NOT do this!) (a) Draw a circuit diagram to represent the situation.(b) If the internal resistance of the power supply is, what is the current through his body?(c) What is the power dissipated in his body?(d) If the power supply is to be made safe by increasing its internal resistance, what should the internal resistance be for the maximum current in this situation to be 1.00 mAor less?(e) Will this modification compromise the effectiveness of the power supply for driving low-resistance devices? Explain your reasoning.
Aammeter is placed in series with aresistor in a circuit. (a) Draw a circuit diagram of the connection. (b) Calculate the resistance of the combination. (c) If the voltage is kept the same across the combination as it was through theresistor alone, what is the percent decrease in current? (d) If the current is kept the same through the combination as it was through theresistor alone, what is the percent increase in voltage? (e) Are the changes found in parts (c) and (d) significant? Discuss.
Some light bulbs have three power settings (not including zero), obtained from multiple filaments that are individually switched and wired in parallel. What is the minimum number of filaments needed for three power settings?
A \(240{\rm{ }}kV\) power transmission line carrying \(5.00 \times {10^2}\;A\)is hung from grounded metal towers by ceramic insulators, each having a \(1.00 \times {10^9}{\rm{ }}\Omega \) resistance. Figure \(21.51\).
(a) What is the resistance to ground of \(100\) of these insulators?
(b) Calculate the power dissipated by \(100\) of them.
(c) What fraction of the power carried by the line is this? Explicitly show how you follow the steps in the Problem-Solving Strategies for Series and Parallel Resistors.
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