Searching for Series and Parallel Circuits. Observe and Design Draw circuit diagrams according to the word descriptions below. Build the circuits and use the symbols to represent the battery and the light bulbs. Circuit Description One 2.0-V battery, one lighted light bulb, and wires Draw a Circuit Diagram One 2.0-V battery, two lighted light bulbs in series, and wires One 2.0-V battery, two lighted light bulbs in parallel, and wires 2. Reason In the previous class you learned of two analogies that can be used to describe circuits. Identify what the moving electrons, battery, connecting wires, and light bulbs using one of the two analogies learned. Using the same analogy, describe the situations: when batteries are in series, the light bulb is brighter; when identical batteries are in parallel, the light bulb is the same brightness.
Construct the following series and parallel circuits in the Circuit Construction Kit. After building each circuit, use the ammeter and voltmeter to measure the current in the wires and the across each light bulb in the simulated circuit. What patterns do you come up with as you build the circuits? Note: When finding the total for the entire circuit ( V total ) we are not looking for the sum of all the voltmeter readings. Instead, find the across the entire circuit, as shown in the diagrams below. When finding the total current ( I Total ) we are again not looking for the sum of all the ammeter readings, but the total current for the entire circuit. 3. each Ammeter Difference across each element current V 4. each Ammeter Difference Across each DV battery = DV = V V total across bulbs DV 2 = DV total across bulbs = 2 V 2 current
5. Current through Each Ammeter I 3 = A 3 Difference Across each V 2 = _ V 2 V 2 V total V total = current 6. each Ammeter I 3 = I 4 = A 3 Difference Across each V 2 = V 3 = V 2 V 2 A 4 V total current V total = 3 V 3
7. each Ammeter I 3 = V Difference Across each V 2 = V 3 = V total = 2 V 2 A 3 3 V 3 V total current 8. Each Ammeter Difference Across each current V batteries = V 9. Each Ammeter Difference Across each V batteries = V current
0. Summarize your findings: Series Parallel Batteries: Batteries: light bulbs: light bulbs across light bulbs: Difference across light bulbs: Circuit Junctions Develop a rule for the current going into and coming out of a junction. Circuits Loops Develop a rule for the of all elements in a loop. Did you know? s in Series: When circuit elements are connected in series, the current through each element is the same and the across the elements is the sum of the s across each element: I 3 = I total V + V 2 + V 3 = V total s in Parallel: When circuit elements are connected in parallel, the is the same across each element and the total electric current is the sum of the currents through each element: V = V 2 = V 3 = V total I + I 2 + I 3
Homework. Complete the following activity. a. Rank the bulbs in the circuit shown to the above according to their brightness when the switch is open. b. Now rank the bulbs in the circuit when the switch is closed. c. Predict how the brightness of each of the first three bulbs changes after the switch is closed. d. Test your prediction using the PHET Circuit Construction Kit and write your conclusions. 2. Answer the following in a brief paragraph: Jim says that a battery is a source of constant current. Do you agree or disagree with Jim. If you agree what arguments do you have to support his opinion? If you disagree, how can you convince Jim in you opinion. In general, what does it take to convince somebody in physics?