Lab 6 Lab Circuit-Resistors - Bulbs XXXXXXXXXXName _____________________
Lab Goal:
To understand how circuits function with resistors and bulbs in series and parallel.
Learn to use ammeters and voltmeters especially how to connect them into a circuit.
Look at the effects of series and parallel circuits
Confirm equivalence rules
https:
phet.colorado.edu/en/simulations/circuit-construction-kit-dc-virtual-lab
For this lab you will explore both the simulation AND the elements in your kit.
Voltmeters measure potential (available electric energy)
Ammeters measure cu
ent (charges moving in interval of time)
Detectors are devices with their own circuits so you do not want the detector to affect the reading
1. If the ammeter detects the cu
ent in the circuit where do you think is the proper position to connect the ammeter?
2. If the voltmeter tests the energy drop across the circuit element where do you think is the proper position to connect the voltmeter?
I. Observing voltage relationships 
Go to the PHeT web site and use the Circuit Construction Kit simulation (CCK). Drag out three batteries. Measure the voltage of each using the voltmeter and record the voltage in a table like the one shown. Then move the batteries end to end as below to measure combined voltage. 

Battery
Voltage (V)
1
2
3
1+2
1+2+3
Describe the relationship between the number of batteries and the voltage. Write a mathematical expression that shows your observation.

II. Using voltage
Use the PhET simulation to build a circuit with a battery and a light bulb.
a. Draw what your circuit looks like. 

. How does the voltage of the battery compare to the light bulb voltage?
(Use the voltmeter to measure these two circuit elements)
Explain what you think is happening. Use Kirchoff Law concepts (conservation of charge and energy)
c. Vary the voltage of the battery (choose 2 or 3 different voltages; some lower and some greater that the original voltage) and write observations about how the
ightness is
affected by voltage.
d. Think about a real light bulb and battery; explain what you think is happening that causes the changes in
ightness.
III. Using voltage in series circuits
Build the circuits below in the PhET sim with a battery at about 12 volts and light bulbs. Turn on the voltmeter and ammeter to measure voltage of the battery and cu
ent into it. Record bulb
ightness with descriptive language.
# of bulbs
Battery voltage
XXXXXXXXXXV)
Cu
ent into
Battery (A)
Brightness of Bulbs
1
2
3
1. Summarize the relationships you observed relating the Battery Voltage and the Brightness of Bulbs. Explain what you think is happening.

2. Test to see if changing the battery voltage causes you to modify any of your conclusions.
(Use 2 different voltages (larger and smaller that original)
3. Test using the voltmeter or ammeter in different ways.
a. Does it matter if you take the reading on the left or right of the battery?
b. Switch the meter ends? Describe your tests and results.
IV. Using voltage in parallel circuits
Build the circuits in figures 4-6 for the circuits.
# of bulbs
Battery voltage
XXXXXXXXXXV)
Cu
ent into
Bulbs (A)
Brightness of Bulbs
1
2
3
Summarize the relationships you observed relating the Battery Voltage and the Brightness of Bulbs. Explain what you think is happening.

V. Observing voltage and cu
ent relationships with resistors
Build the circuit below with the PhET sim. Vary the voltage of the battery. Record the battery voltage and the cu
ent in the circuit in a table. Plot the V vs I.
Battery voltage
(V)
Cu
ent into Resisto
1
2
3
4
How are cu
ent and battery voltage related? What is the shape of the graph? 

VI. Series Circuit 
Construct the circuit in figure 1 using the PhET simulation.
a. Make the resistors have different value and record the value of each resistor.
b. Use the ammeter, moving it to take readings in the different places as seen in figure 2.
c. Then use the voltmeter to take voltage readings.
d. Calculate R using Ohm’s Law (V=IR) for the total resistance in last column. 

Resisto
Voltage (V)
Cu
ent (A)
Resistance
1
2
3
Total
Vtotal reading
Atotal reading
RT = VT/IT
How is the total resistance related to the individual resistances?
How is the total cu
ent related to the individual cu
ents?
How is the total voltage related to the individual voltages?
VII. Parallel Circuits Construct the circuit in figure 1 using the PhET simulation.
a. Use the same value resistors that you used in Part VI (Series Circuits).
b. Take readings in different places shown in figure 2 by moving the meters.
c. Use the table below. Fill in your measurements and calculate total resistance
XXXXXXXXXXusing Ohm’s Law (V=IR) and enter that value in the last column.
Resisto
Voltage (V)
Cu
ent (A)
Resistance
1
2
3
Total
Vtotal reading
Atotal reading
RT = VT/IT
a. How is the total resistance related to the individual resistances? Explain what you think is happening.
. Look up the mathematical relationship for finding total resistance in a parallel circuit. Show that your data fits the equation.