INTRODUCTION TO ENGINEERING
ELECTRIC CIRCUITS LAB
Given the diagrams below, make a sketch of a series and parallel circuit to test in class the next
day. Open dots are nails with which to aid you in your circuits.
Series Circuit
Parallel Circuit
LAB ACTIVITY
Materials to be provided by instructor: insulated wire, electrical tape, and work board
Materials to be provided by students: 2 flashlights with 2 working D-cell batteries
SERIES CIRCUIT
1.
2.
3.
4.
5.
Observe brightness of one lamp in series with the 2 D-cell batteries taped together.
Measure the voltage across the lamp.
Repeat step 1 with two lamps.
Repeat step 1 with three lamps.
Estimate how many lamps can be put in series before illumination can no longer be
observed. Why?
BONUS. Given a 12-volt DC voltage source, what is the maximum number of bulbs that
can be placed in series if each bulb requires a minimum of 20 mA to illuminate? Assume
each bulb is 50 .
PARALLEL CIRCUIT
1.
2.
3.
4.
Observe brightness of one lamp in parallel with the batteries. Measure the voltage across
the lamp.
Repeat step 1 with two lamps.
Repeat step 1 with three lamps.
Disassemble your flashlight. Re-build your flashlight without the casing.
PARALLEL AND SERIES CIRCUITS
Using your engineering (McGuyver) creativity, solve the following scenarios.
1.
It is dark out. You are all alone and are being followed by a bad guy. All you have with
you is one working flashlight, one dead battery flashlight, wire, and tape. If you could
make your pursuer think you suddenly had a friend join up with you, he would probably
leave you alone, thinking he was outnumbered. Make two bright flashlights to try to fool
your attacker.
2.
Now you are ready to counter-attack. You want to make the bad guy think you are hiding
in a tent with your supposed friend and your flashlight batteries are going dim. Try
making three or four dim lights to really confuse the guy.
3.
What if all you had was aluminum foil instead of wire?
CONCLUSIONS
1.
2.
3.
Describe how a series circuit works.
Describe how a parallel circuit work.
With multiple bulbs, why does a parallel circuit give brighter illumination than a series
circuit?