Home
Overview
Organizing Your Lab
Lesson 1
A Simple Electric Circuit
Lesson 2
A Series Circuit
Lesson 3
A Parallel Circuit
Lesson 4
Cells & Batteries Sources in Series and Parallel
Lesson 5
Resistance - Ohm’s Law
Lesson 6
Canadian Electricity Alternatives
Course Facilitator & FAQ's
Expectations
Acknowledgements
Downloadable student notes (.doc .wpd .pdf )
Downloadable answers to student notes (.doc .wpd .pdf )
Modeling A Series Circuit |
Start with a demonstration of a series circuit as shown in the student notes. Without explaining anything first connect only one bulb, then add another in series in order the students can observe that each bulb gets dimmer. Now use the model to explain.
Wooden Block Model
Remind the students that one coulomb falling through a distance of 1 volt has enough energy to get the student light bulb once around. Therefore a voltage drop of ½ Volt, the student/load only has enough energy in each coulomb to turn half way around.
The "wires" (Student conductors) pass the blocks along at shoulder level. If the first bulb uses all the coulombs energy by dropping them to waist level, the wires at that point in the circuit pass the blocks along at waist level. If the positive battery box is at waist level, then, the second bulb CANNOT get any energy because it receives the coulombs at the same level it has to release them. Therefore the second bulb can not get enough energy to move and the current stops.
Students are challenged: "How can we change things to get the blocks to go through BOTH bulbs?" We know that it must happen because of the demonstration this lesson started with. The answer we want, of course, is that the first bulb should finish half-way down to his waist. The next bulb can then start half-way down and finish at the waist. Wires cannot lift blocks into the positive box, so this is the only solution that works with out increasing the potential across the battery.
With a voltage drop of ½ Volt, the student/load only has enough energy in each coulomb to turn half way around. They must receive the next coulomb with their other hand. This is difficult but has the advantage of slowing the current down. With less energy the student bulb can not spin as fast and hence must give off less light.
Question "SO how will each bulb appear compared to a one bulb circuit as it gives off light energy? What do you think would happen if another bulb were added" The answer we want, is that they will appear dimmer.
Observations
Since each coulomb only falls through ½ volt, the student/load only has enough energy in each coulomb to turn half way around. With less energy the student bulb can not spin as fast, hence must give off less light. This also causes the current to slow down when more bulbs are connected in series.
The "voltage" of the battery (potential gain) has remained one volt, the voltage drop across each bulb is ½ Volt. Total Voltage gain equals total voltage drop.
Practice Connecting Circuits & Drawing Schematic Diagrams
The student learns to keep all circuit components in the same relative position with these practice questions. They are arranged to develop this habit without the student being aware of it.
REALITY CHECK - Wiring Real Circuits
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