Electricity Lab – Exploring Series Circuits
Physics
Names:
Date:
Safety: Never close a circuit until a teacher has approved it.
Never rewire or adjust any
element of a closed circuit. Never work with electricity near water; be certain the floor and all
work surfaces are dry.
Objectives:
 Construct series circuits using different combinations of bulbs, wires, and resistors.
 Observe the effects of an electric current.
 Compare your observations from different trials to discover how relationships are
affected by changing one or more variables.
 Classify and analyze your observations.
Materials:
2 Batteries
3 Miniature Christmas tree lamps
1 Knife switch
1 Resistor
Connecting wires
Answer the all the following questions on a separate sheet of paper.
Pre-lab questions
1. Define the following terms:
a. Schematic diagram
b. Series circuit
c. Equivalent resistance
d. Current
2. In series circuits…
a. What is the equation for equivalent resistance?
b. What is the equation for potential difference?
3. What is special about current and resistors in series?
Procedures
Part I
1. Draw a schematic diagram of a series circuit with the following components: 1 EMF
source, 2 lamps, and 1 switch, connected with wires.
2. Obtain the needed materials and build the circuit you have just drawn. When complete, show
your teacher.
3. Did the bulbs both light up? How did the brightness of each lamp compare? How
could you make both bulbs light up if they did not?
4. Using the multimeter, measure the current of the circuit, total resistance of the circuit, and the
potential difference of the battery alone. Next use the multimeter to measure the resistance of
all components and wires in the circuit. Record your readings in the Part I data table.
5. For the circuit you just built, calculate the following…(be sure to show all work)
a. Equivalent resistance for the circuit
b. Current for the entire circuit, and for each resistor
c. Voltage across each resistor
6. How did your measurements with the multimeter compare to the calculated value for the
equivalent resistance and current? Higher, lower? Explain your results.
7. If you remove one of the bulbs, and reconnect the circuit. What happens to the
brightness of the other bulb? Should the new equivalent resistance be higher or lower? Why?
Should the new current be higher or lower? Why?
Part II
8. Draw a schematic diagram of a series circuit with the following elements: 2 EMF
sources, 3 lamps, 1 switch, and 1 resistor, connected by wires.
9. Obtain the needed materials and build the circuit you have just drawn. When complete, show
your teacher.
10. Using the multimeter, measure the current of the circuit, total resistance of the circuit, and the
potential difference of each battery alone. Next use the multimeter to measure the resistance
of all components and wires in the circuit. Record your readings in the Part II data table.
11. How does the brightness of each lamp compare?
12. For the circuit you just built, calculate the following…(be sure to show all work)
a. Equivalent resistance for the circuit
b. Current for the entire circuit, and for each resistor
c. Voltage across each resistor
13. How did your measurements with the multimeter compare to the calculated values? Higher,
lower? Explain your results.
Post-lab Questions
1. What would have happened if you had disconnected any wire or opened the switch in
either of the circuits?
2. In general, what happens to the current when a resistor is removed from the circuit?
3. What was the most difficult part of this activity? Why?
4. Based on your observations, what would happen to the brightness of the bulbs if you
added two more bulbs to either circuit? Explain your reasoning.
5. Suppose that a light bulb provides resistance to the current. How does using more than
one light bulb affect the total resistance of the entire circuit? How does it affect the
total current?
6. Does the order of resistors, bulbs, batteries, switches, etc. matter when calculating the
resistance, voltages, currents, bulb brightness? Why or why not?
7. What are 2 reasons why using a series circuit would be advantageous?
8. What are 2 situations where using a series circuit would NOT be advantageous?