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PROBLEM SOLVING QUESTIONS


Answer the following questions using the Ohms Law Program simulation.

This program was developed by Greg Von Fange at the Technology Center of DuPage (TCD)


  • Holding I constant, make the voltage 50V. What is the resistance? What is the power?
  • Repeat the above procedure increasing the voltage to 75, 95, 110, 125, 140, 160 and 175V.
  • Plot a voltage vs resistance graph. Comment on the observed pattern.

   

CRITICAL THINKING

A.

Now think about the relationship between the current, voltage and resistance. Sketch a graph showing what would happen to the voltage if the current was doubled? What would the resistance be if the current was doubled?

B.

Below is a simplified schematic of the heater blower motor in a car.  The switch can connect the circuit to each of the three pathways.  The low pathway contains all three resistors in series.  The medium pathway contains just two of the resistors.  The high pathway only passes through one resistor.  Use what you know about Ohm’s law to explain why the heater blower motor runs at a different power on each of these settings.


 


C.

Joe and Mark are working on a car with a bad fuel injector.  Mark has replaced the bad fuel injector, but the computer still returns a code for failing fuel injector.  Joe noticed that the insulation in the fuel injector had been corroded by the gasoline.  Joe tells Mark that he thinks they might have fried the driver for the fuel injector.  He remembered that the fuel injector is a solenoid with a wire wrapped many times.  When the insulating plastic is corroded the solenoid basically becomes one piece of metal and the resistance becomes close to zero.   Mark wants to know what the resistance has to do with frying the driver?  Can you use Ohm’s law to tell Mark what happened?

D.

Household voltage varies around the world.  Japan uses 100 volt, and in the US we have a standard voltage of 110 volt.  Some other countries don’t even have a standard voltage.  The voltage in France varies from 110-360 volts.  What would happen if you plugged a 110 volt hair dryer from the US into a 240 volt outlet in England?  Explain your answer using Ohm’s Law.


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