PURPOSE:
To expose the student to new equipment and lab procedures. And to test the different aspects of Ohm's Law.

INTRODUCTION:
Ohm's Law defines the relationships between (V) voltage, (I) current, and (R) resistance. One ohm is the resistance value through which one volt will maintain a current of one ampere.

I = V / R

( I ) Current is what flows on a wire or conductor like water flowing down a river. Current flows from negative to positive on the surface of a conductor. Current is measured in (A) amperes or amps.

( V ) Voltage is the difference in electrical potential between two points in a circuit. It's the push or pressure behind current flow through a circuit, and is measured in (V) volts.

( R ) Resistance determines how much current will flow through a component. Resistors are used to control voltage and current levels. A very high resistance allows a small amount of current to flow. A very low resistance allows a large amount of current to flow. Resistance is measured in ohms.

An ammeter can be used to measure the current within a circuit. The ammeter is placed in series with the circuit actually becoming a part of the circuit. The ammeter has almost no resistance and thus does not change the dynamics of the circuit. A voltmeter can be used to determine the voltage at any given part of the circuit. The voltmeter is placed in a parallel configuration to the circuit but since it has an extremely high resistance, the dynamics of the circuit is not changed. During this lab you will determine the resistance of three different resistors and then measure current and voltage at different points within a circuit which these resistors become a part.

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A Voltmeter and Ammeter is provided to measure voltage and current respectively. The voltmeter displays values in volts while the ammeter displays amps.

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The source of electrical current for this lab is provided by 1 to 4 dry cell batteries (depending on your lab). The batteries are hooked up in series so their volt values are added.

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Three resistors of unknown value will be used in this lab.

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If you get into trouble and perform some procedure that causes the lab to fail(lab equipment will no longer operate), you can press the "Reset" button and the simulation will return to the starting position.

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PROCEDURE:

1) You can adjust the background shading by clicking on the "Special" button to the right and selecting "Background". Click on the "Special" button and select "Print Blank Report" to obtain a web page that can be printed and used as a lab report. (the program will not be interrupted)

2) The source of the electric current within this lab is provided by one or more 1.5 volt batteries located at the top of the screen. Although their ratings are noted as 1.5 volt, in reality they will vary from that value. Turn on the voltmeter by clicking on the button at the base of the unit and move it closer to the circuit diagram. Drag the black clip from the voltmeter over to the clip marked "a" and attach it (just release it). Now drag the red clip from the voltmeter over to the far right bottom of the screen and attach it to the clip marked "h". Record the voltmeter value in volts. This is the voltage of the circuit. Release the two voltmeter clips.

3) Turn on the Ammeter and move it closer to the circuit. The circuit diagram has the letter "A" in a circle near the bottom of the screen. This is a symbol that indicates where the ammeter should be attached. Attach the ammeter's black clip to clip "g" and the red clip to clip "h". Since at this time the circuit is not complete, a reading of 0 should be noted.

4) Make sure the wire "jumper" is in place by dragging it to the right. This closes the upper part of the circuit. There are three positions that resistors can take in the circuit. They are labeled "1", "2" and "3" and have a light gray rectangle around their location. Along side of the rectangle is the symbol for a resistor. Drag resistor "A" over and drop it into the rectangle symbol marked "2". It should clip in place and you should get a reading on the ammeter. Record this reading as shown in amps. Put the resistor "A" back and place resistor "B" in its place. Record the reading. Lastly record the value for resistor "C". Put resistor "C" back.

5) Slide the "jumper" over to the left and open up the circuit between "a" and "b". Place resistor "A" in slot "1" and resistor "B" in slot "2". Record the value on the ammeter. These two resistors and now in a series configuration. Put the resistors back.

6) Slide the "jumper" over to the right and close the circuit between "a" and "b". Place resistor "A" in slot "2" and resistor "B" in slot "3". Record the value on the ammeter. These two resistors and now in a parallel configuration. Put the resistors back.

7) Slide the "jumper" over to the left and open up the circuit between "a" and "b". Place resistor "C" in slot "1", "A" in slot "2" and resistor "B" in slot "3". Record the value on the ammeter. The resistors are in a combination series and parallel configuration. Keep the resistors in this position for the next procedure.

8) Connect the voltmeter's black clip to clip "a" above resistor "C". Connect the red clip to clip "b" below resistor "C". This now measures the voltage across resistor "C" in this circuit. Record the voltage. Move the voltmeters clips to clips "c" and "e" across resistor "A". Record the voltage. Move the voltmeters clips to clips "d" and "f" across resistor "B". Record the voltage. NOTE: if you get a negative voltage, reverse the voltmeters clips.

9) Calculate the requested values asked for on the lab sheet and any given by your teacher. For help on these values click on the "Special" button and select "View Data & Hints". Select "File Report" to send a copy to be viewed by your teacher.