Voltage Lab

Description

Include answers to all questions below with a ??.

Upload all your answers in a document (MS Word/Google Doc/Pages/…)

• Some questions involve taking a picture and putting it in the document.

If you don’t have a lab kit: for now do it using this simulation (Links to an external site.).

Show your work for each answer where you do a calculation. (include the equation and the values & units for each quantity)

• Very Helpful videos: Video 1 (Links to an external site.) on using Multimeter, Video 2 (Links to an external site.) with extra details

<strong>PART I: Resistors</strong>

• Take out the components from your lab kit.

Remember the things we learned in the Lab Intro:

• Ohm’s Law: ?=??V=IR.

Resistors in Series: ???=?1+?2+…Req=R1+R2+…

Resistors in Parallel: 1???=1?1+1?2+…1Req=1R1+1R2+…

• ?? What is the voltage of your battery? (measure it)

?? To make sure you don’t break the multimeter we’re going to calculate the minimum resistance that we can connect to the battery. If you want a maximum possible current of 150 mA, what is the smallest resistance you can attach to your battery?

Make sure that the equivalent resistance you attach to your battery is always at least the value you found in the last question.

Choose any two identical resistors.

• ??Measure their resistances (they should be about the same). What are they?

Put the two identical resistors in series (NO BATTERY yet) like this:

??What is the predicted value of the equivalent resistance(??Rp)?

??What is the actual equivalent resistance you measure(??Re)?

??Calculate the percent error of the measure value from the predicted value:

%?????=???????????×100%error=|Re?Rp|Rp×100.

1. Choose any two different resistors (but not TOO different)
2. ??Measure their resistances. What are they?

Put the two resistors in series (NO BATTERY yet) like this:

• ??What is the predicted value of the equivalent resistance(??Rp)?

??What is the actual equivalent resistance you measure(??Re)?

??Calculate the percent error of the measure value from the predicted value.

Choose any two identical resistors.

??Measure their resistances. What are they?

Put the two resistors in parallel (NO BATTERY yet) like this:

??What is the predicted value of the equivalent resistance(??Rp)?

??What is the actual equivalent resistance you measure(??Re)?

??Calculate the percent error of the measure value from the predicted value:.

Choose any two different resistors 

??Measure their resistances. What are they?

Put the two resistors in parallel (NO BATTERY yet) like this:

??What is the predicted value of the equivalent resistance(??Rp)?

??What is the actual equivalent resistance you measure(??Re)?

??Calculate the percent error of the measure value from the predicted value.

??Call in the instructor (aka His Illustriousness Sébastien of House Cormier) to check your work

• <strong>PART II: Simple Resistor Circuit</strong>

??  Create Circuit 1 (shown below) using a 20 ohm resistor, your battery, the switch (leave the switch open), and the Ammeter (which is the multimeter set up to measure current).  Take a picture of your physical circuit setup and include it here.
NOTE: Always check the values of resistors before putting them in the circuit using the Multimeter in Ohmmeter mode.

 ?? Circuit 1

?? What is the expected current in this circuit based on Ohm’s Law?

?? What is the actual current when you close the switch? (don’t forget to open the switch after you measure)

?? Move the Ammeter in the circuit so that is between the switch and the resistor. What is the current now (when the switch is closed)?

?? How do the answers of #6 and #7 compare? Are the answers consistent with your understanding of current?

Remove the Ammeter and rebuild the circuit as shown below

 ?? Circuit 1 (without the Ammeter)

?? Change the multimeter to Voltmeter mode (using the 2000 mV range). Close the switch. What is the voltageacross (i) the battery, (ii) the switch), and (iii) the resistor?  NOTE: Remember the battery voltage is positive  and theother ones are negative  or zero .

?? What does the sum of the voltages add up to? Is it as expected? Explain. 

Open the switch

<strong>PART III: 2 Resistor Series Circuit</strong>

??Set up Circuit 2 (2 resistors in series) shown below using a 100 ohm resistor and a 20 ohm resistor. (in all cases, if you don’t have the required resistors use the closest resistors you have. Take a picture of your physical circuit setup and include it here.

 ?? Circuit 2 

?? Calculate the expected equivalent resistance of this circuit.

?? Measure the actual equivalent resistance of this circuit. (make sure the switch is off for this part)

?? What do you expect the current to be  (i) through the battery, (ii) between the resistors?

?? Measure the current at those two points. Is it as expected?

?? What do you expect the voltage drop across each resistor to be? Explain.

?? Measure the voltage across each resistor.  Is it as expected?

Open the switch

<strong>PART IV: 2 Resistor Parallel Circuit</strong>

??Set up Circuit 2 shown below using a 100 ohm resistor and a 20 ohm resistor. This is 2 resistors in parallel. Take a picture of your physical circuit setup and include it here

 ?? Circuit 3 

?? Calculate the expected equivalent resistance of this circuit.

?? Measure the actual equivalent resistance of this circuit. (make sure the switch is off for this part)

?? What do you expect the current to be through (i) the battery, (ii) the 100 ohm resistor (iii) the 20 ohm resistor?

?? Measure the current at those three points. Is it as expected?

?? What do you expect the voltage drop across each resistor to be? Explain.

?? Measure the voltage across each resistor.  Is it as expected? 

Open the switch

<strong>PART V: Equivalent resistance of a 4 Resistor Circuit</strong>

We’re just using resistors and wires for this one: Make up your own circuit using 4 resistors (make sure to choose 4 resistors that aren’t too different from each other and don’t just put them all in series! )

?? Draw a circuit diagram. Include a picture of your circuit diagram here. 

?? Calculate the expected equivalent resistance of this circuit. (using resistor addition formulas)

?? Measure the actual equivalent resistance of this circuuit.

If you don’t have a lab kit: for now do it using this simulation (Links to an external site.).