3.4.4 Lab: Circuit Building
Dry Lab
Physics Honors Sem 2
Name:
Dhruva Yerabati
Date:
8/19/24


Circuit Building

Materials:
Circuit building activity from unit
Graph paper

Materials for Exploring Further: 


Simple plug-in night-light
Electrostatics kit (plastic rod and electroscope)
Small piece of wool
Horseshoe magnet
Cathode ray tube
Bar magnet
Container of iron filings
White craft paper
Magnetic compass
In this lab, you will investigate the relationships among voltage, current, and resistance in series and parallel circuits. 
Procedure 

Part 1: Series Circuit with Two Resistors, Designed in Terms of Resistance 

1. Design a circuit that has two resistors connected in series. Given that you have a 20 V battery, choose resistors that will produce a current of 0.2 A. Record the resistance in data table 1. 

Using the flash animation available on the launch page of the lab activity, construct a series circuit according to the specifications. Represent your circuit on graph paper, labeling each element in the circuit. Calculate the current through and voltage drop across each resistor, and record in data table 1. 

2. Using the ammeter and voltmeter, determine the current through and voltage drop across each resistor by touching leads to the wires before and after each individual resistor. Record the values in data table 1. 

Data Table 1: Series Circuit with Two Resistors, Designed in Terms of Resistance


Resistance (Ω)
Calculated 
voltage (V)
Experimental 
voltage (V)
Calculated 
current (A)
Experimental 
current (A)
60


12


12


0.2


0.2


40


8


8


0.2


0.2






Part 2: Parallel Circuit with Two Resistors, Designed in Terms of Resistance 

3. Design a circuit that has two resistors connected in parallel. Given that you have a 20 V battery, choose resistors that will produce a current of 1.5 A. Record the resistance in data table 2. 

Using the flash animation available on the launch page of the lab activity, construct a parallel circuit according to the specifications. Represent your circuit on graph paper, labeling each element in the circuit. Calculate the current through and voltage drop across each resistor, and record in data table 2. 

4. Using the ammeter and voltmeter, determine the current through and voltage drop across each resistor. Record the values in data table 2. 

Data Table 2: Parallel Circuit with Two Resistors, Designed in Terms of Resistance


Resistance (Ω)
Calculated 
voltage (V)
Experimental 
voltage (V)
Calculated 
current (A)
Experimental 
current (A)
40


20


20


0.5


0.5


20


20


20


1.0


1.0





Part 3: Series Circuit with One Resistor, Designed in Terms of Potential Difference (Voltage) 

5. Design a circuit that has a single resistor connected in series. Given that you have a 100 Ω resistor, calculate a power source voltage that will produce a current of 0.4 A. 

Use the instructions provided in step 1 to build the circuit. 

6. Calculate the current through and voltage drop across the resistor, and record the values in data table 3. 

7. Using the ammeter and voltmeter, determine the current through and voltage drop across the resistor. Record the values in data table 3. 

Data Table 3: Series Circuit with One Resistor, Designed in Terms of Potential Difference (Voltage)


Resistance (Ω)
Calculated 
voltage (V)
Experimental 
voltage (V)
Calculated 
current (A)
Experimental 
current (A)
100


40


40


0.4


0.4





Part 4: Parallel Circuit with Two Resistors, Designed in Terms of Potential Difference (Voltage) 

8. Design a circuit that has two resistors connected in parallel. Given that you have a 22.5 Ω equivalent resistance, calculate a power source voltage that will produce a current of 0.8 A. Record the resistance and voltage in data table 4. 

Use the instructions provided in step 1 to build the circuit. 

9. Calculate the current through and voltage drop across each resistor, and record the values in data table 4. 

10. Using the ammeter and voltmeter, determine the current through and voltage drop across each resistor. Record the values in data table 4. 

Data Table 4: Parallel Circuit with Two Resistors, Designed in Terms of Potential Difference (Voltage)


Resistance (Ω)
Calculated 
voltage (V)
Experimental 
voltage (V)
Calculated 
current (A)
Experimental 
current (A)
30


18


18


0.6


0.6


45


18


18


0.4


0.4





Part 5: Series Circuit with Two Resistors with Unknown Current 

11. Design a circuit that has two resistors connected in series. Use one 60 Ω resistor, one 20 Ω resistor. Connect these two resistors to a 20 V battery. 

Use the instructions provided in step 1 to build the circuit. 

12. Calculate the current through and voltage drop across each resistor, and record the values in data table 5. 

13. Using the ammeter and voltmeter, determine the current through and voltage drop across each resistor. Record the values in data table 5. 

Data Table 5: Series Circuit with Two Resistors, Effect of Individual Resistors


Resistance (Ω)
Calculated 
voltage (V)
Experimental 
voltage (V)
Calculated 
current (A)
Experimental
current (A)
R1 = 60
15


15


0.25


0.25


R2 = 20
5


5


0.25


0.25





Part 6: Parallel Circuit with Two Resistors with Unknown Current 

14. Design a circuit that has two resistors connected in parallel. Use one 100 Ω resistor and one 30 Ω resistor. Connect these two resistors to a 20 V power source. 

Use the instructions provided in step 1 to build the circuit. 

15. Calculate the current through and voltage drop across each resistor, and record the values in data table 6. 

16. Using the ammeter and voltmeter, determine the current through and voltage drop across each resistor. Record the values in data table 6. 

Data Table 6: Parallel Circuit with Two Resistors, Effect of Individual Resistors


Resistance (Ω)
Calculated 
voltage (V)
Experimental 
voltage (V)
Calculated 
current (A)
Experimental 
current (A)
R1 = 100












R2 = 30















Part 7: Series Circuit with One Resistor, Designed in Terms of Current Through Electric Circuit Elements

17. Design a circuit that has a single resistor connected in series. Choose a resistor that will provide 20 W of power from a 40 V power source. 

Use the instructions provided in step 1 to build the circuit. 

18. Calculate the current through and voltage drop across each resistor, and record the values in data table 7. 

19. Using the ammeter and voltmeter, determine the current through and voltage drop across each resistor. Record the values in data table 7. 

Data Table 7: Series Circuit with One Resistor, Designed in Terms of Current Through Electric Circuit Elements


Resistance (Ω)
Calculated 
voltage (V)
Experimental 
voltage (V)
Calculated 
current (A)
Experimental 
current (A)






40



0.5



Part 8: Parallel Circuit with Two Resistors, Designed in Terms of Current Through Electric Circuit Elements 

20. Design a circuit that has two resistors connected in parallel. Choose resistors that will each provide 5 W of power from a 20 V power source. 

Use the instructions provided in step 1 to build the circuit. 

21. Calculate the expected current through and voltage drop across each resistor, and record the values in data table 8. 

22. Using the ammeter and voltmeter, determine the current through and voltage drop across each resistor. Record the values in data table 8. 

Data Table 8: Parallel Circuit with Two Resistors, Designed in Terms of Current Through Electric Circuit Elements


Resistance (Ω)
Calculated 
voltage (V)
Experimental 
voltage (V)
Calculated 
current (A)
Experimental 
current (A)


































Part 9: Open Circuit Investigation


23. Construct a simple series circuit with one resistor. Use the circuit building interactive linked on the Dry Lab page of this activity to answer question 24. 

24. Use the voltmeter and ammeter to determine the voltage and current of the circuit. Open the switch, and again measure the voltage and current of the circuit. 

What happened to the voltage and current after the switch was opened?












Part 10: Use of Power by Lightbulbs Investigation


25. Design a simple circuit using one lightbulb and the instructions from step 1. Set the power source at 20 V. Use the ammeter to determine the total current in the circuit as an indication of its use of power. 

What happens to the bulbs’ use of power if you add a second bulb with the same resistance in series with the first?





Remove the second lightbulb, and then design a parallel circuit using two lightbulbs that have the same resistance. How does the use of power in the parallel circuit compare to the use of power in the simple circuit with one bulb?





26. Suppose you have a circuit with two lightbulbs that have the same resistance connected in series and you have another circuit with two lightbulbs with the same resistance connected in parallel. What would happen if you disconnected one bulb in each circuit?









Using a fixed 20 V from the power source and three lightbulbs that have the same resistance, how would you design a circuit that would allow at least one bulb to use maximum power (have maximum brightness)?













27. Test your idea by constructing the circuit. Record your observations of the power usage along different parts of the circuit below.












Analyze

1. What happens to the current provided by a power source as more resistors are connected in series?









2. What happens to the current provided by a power source as more resistors are connected in parallel?












Draw Conclusions

1. What must be true about the sum of the voltage lost across each resistor connected in series?













2. What happens to the power dissipated by a resistor as the current through the resistor increases?









3. Three lightbulbs are connected in a series. A switch is placed between the first lightbulb and the second lightbulb. If that switch is opened, what happens to each of the three lightbulbs?












Explore Further


Materials:

Part 1:
Simple plug-in night-light

Part 2:
Electrostatics kit (plastic rod and electroscope) 
Small piece of wool

Part 3:
Horseshoe magnet
Cathode ray tube

Part 4:
Bar magnet
Container of iron filings
White craft paper
Magnetic compass


Part 1: Household Circuit Field Investigation

In this field investigation, you will explore household circuits in which the circuit breaker switches are labeled with the circuits’ location. Flip the switch for one location, then determine what is not working in that area as a result. Test the outlets in that area by plugging in a night-light. Which outlets work? Which do not? Which light switches turn on? Which do not? Which electrical devices may have turned off as a result of the switch being flipped? What do your observations indicate about the circuit design of the household?


















CAUTION: Observe proper field safety guidelines for this study: 


Make sure a teacher or other responsible adult is aware of your plans and has approved your intended studies.
Work with at least one other student.
Ensure that no equipment is operating in the household that would be damaged or would cause an individual harm if it were briefly turned off.

Part 2: Electrostatics Investigation

Rub the plastic rod from the electrostatics kit with the piece of wool. Touch the rod to the electroscope. What happens to the leaves on the electroscope? What does this tell you about the charge on the rod?









Part 3: Cathode Ray Tube Investigation

Set up the cathode ray tube according to instructions for your device. Move the horseshoe magnet around the cathode ray tube. What do you observe?









Part 4: Magnetism Investigation

Roll out a large piece of white craft paper. Lay a bar magnet in the middle of the craft paper. Sprinkle some iron filings around the magnet and observe. Now try the experiment again with a horseshoe magnet instead of a bar magnet. What do the iron filings show you? Now move a magnetic compass to various positions around the magnet. What does the varying position of the compass needle tell you?




















Set up a simple series circuit and connect it to the power source. Plan a way in which to observe the connection between electric charge and magnetic fields and forces. What piece of equipment should you use? What do your observations illustrate about the relationship between moving electric charges and magnetic fields/forces?