PHYS 1415 Lab-07: Series and Parallel Circuits
Name: _________________________
Objectives:
· To explore various a
angements of batteries and bulbs, and the effect of those a
angements on bulb
ightness.
Discussion
Many devices include electronic circuitry, most of which are quite complicated. Complex circuits are made, however, from simple circuits. In this activity, you will build one of the simplest, yet most useful circuits ever invented – that for lighting a lightbulb.
We are going to explore simple circuits using light bulbs connected to a battery. You will be using PhET simulation Circuit Construction Kit: DC - Virtual Lab (https:
phet.colorado.edu/en/simulation/circuit-construction-kit-dc-virtual-lab)
Activity 1: Light bulbs Connected in Series
1. Using one light bulb, one battery, and one wire, try lighting the bulb in as many ways as you can.
2. Upload screenshots of your a
angements for the ones that work.
Question-1: Is it possible to light the bulb using the battery and no wires? Explain.
3. Connect one bulb to one battery as shown in Figure 1. This a
angement is often refe
ed to as a simple circuit.
XXXXXXXXXXFigure 1
4. Connect the bulbs, batteries, and wires as shown in Figure 2. When the bulbs are connected one after the other like this, the result is called a series circuit.
Figure 2
Question-2: How does the
ightness of each bulb in the series circuit compare with the
ightness of the bulb in a simple circuit?
Question-3: What happen if one of the bulbs in a series circuit is removed? (Do this by removing by one end of the wire connection)
5. Set the resistance of each light bulb to the following: R1 = 5 , R2 = 10 , R3 = 15 .
6. To change the resistance value, click on the light bulb and move the slider.
7. Connect the light bulbs in series as shown in the circuit below:
Set the battery voltage to 20 V. Measure the total voltage: VTotal = __________
To measure potential difference or voltage, you do not have to
eak the circuit. The voltage measuring device used is called voltmeter. You must connect the voltmeter leads one on each side of the circuit element. Standard practice is to touch the red lead of voltmeter to the positive terminal of the battery and the black lead to the negative terminal.
8. Use the voltmeter to measure the voltage across each of the light bulbs.
V1 = ________
V2 = _________
V3 = _________
VTotal = V1 + V2 + V3 = ___________
Question – 4: Does VTotal in Step 8 equal VTotal in Step 9?
9. Use the ammeter to measure the cu
ent through each of the light bulbs.
To measure the cu
ent through a part of the circuit, you must
eak open the circuit at the point where you want to measure the cu
ent and insert the cu
ent measuring device called ammeter. That is, disconnect the circuit, put in the ammeter, and reconnect with it in place. Write down the values of these cu
ents below.
I1 = ________ A
I2 = ________ A
I3 = ________ A
Question – 5: Do you notice any pattern in the cu
ents through the light bulbs connected in series? Explain.
Question – 6: Do you notice any pattern in the voltages across the light bulbs connected in series?
13: Put a 4th bulb in series with the other bulbs. R4 = _____________
Question – 7: Do the bulbs seem to burn as
ight as before?
Activity 2: Resistors Connected in Parallel
16. Connect the bulbs, batteries, and wire as shown in Figure below. When the bulbs are connected along separate paths like this, the result is called a parallel circuit.
Question – 8: How does the
ightness of each bulb in the parallel circuit compare with the
ightness of the bulb in a simple circuit?
Question – 9: What happens if one of the bulbs in a parallel circuit is removed?
17. Click on the battery and set the battery voltage to 12 volts. Set the resistance values: R1 = 10 Ω and R2 = 30 Ω
18. Use the ammeter to measure the cu
ent through each of the light bulbs (by placing the ammeter on wire either before or after the light bulb.
Write down the values of these cu
ents below.
I1 = ________ A
I2 = _________A
19. Now measure the total cu
ent flowing from the battery by placing the ammeter next to the battery.
Itotal (from the battery) =________
20. Use the voltmeter to measure the across each of the light bulbs. Write down the values of these voltages below.
V1 = ________ V
V2 = ________ V
Analysis: Complete the following sentences:
Resistors in Series Circuits:
1. The sum of the voltage drops across the individual bulbs is equal to
2. When you put a 4th bulb in the circuit, do you think the cu
ent in the circuit increased, decreased, or stayed the same?
3. Complete the following (based on Step#13): As the cu
ent in the circuit ___________, the
ightness of the bulbs ____________.
Parallel Circuits:
4. As you add more
anches, does the voltage across each
anch increase, decrease, or stay the same?
5. As you add more
anches, does the cu
ent across a previously existing
anch increase, decrease, or stay the same?
6. If you were to decrease the number of
anches to just one
anch, how would the
ightness of the bulb now compare the
ightness when there were three bulbs in parallel?
7. How do you suppose most of the circuits in your home are wired – in series or in parallel? What is your evidence.
8. How do you suppose automobile headlights are wired – in series or in parallel? What is your evidence.
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