Searching for Patterns in Series and Parallel Circuits Use the Circuit Construction Kit on phet.colorado.edu (DC Circuits only) to build the following circuits. fter building each circuit, use the ammeter and voltmeter to measure the current in the wires and the potential difference 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 potential difference for the entire circuit ( V total ) we are not looking for the sum of all the voltmeter readings. Instead, find the potential difference across the entire circuit. 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. 2.1 Series Circuit - Connect 3 bulbs in series. DIGRM using half of a page! another location. Draw it in the diagram and record the new current next to the ammeter in the diagram. c. Use the voltmeter to measure the TOTL potential difference across the circuit and the potential difference across each bulb. Draw the 4 positions of the voltmeter on your diagram, and record the values of the voltage next to the voltmeters in the diagram. Diagram and Patterns for SERIES Circuit
2.2 Parallel Circuit - Connect 3 bulbs in parallel. DIGRM using half of a page! through ECH resistor. Draw it in the diagram and record each current next to the ammeter in the diagram. c. Use the voltmeter to measure the TOTL potential difference across the circuit and the potential difference across each bulb. Draw the 4 positions of the voltmeter on your diagram, and record the values of the voltage next to the voltmeters in the diagram. Diagram and Patterns for PRLLEL Circuit
2.3 Combo Circuit - Build a combination circuit. DIGRM using half of a page! through ECH resistor. Draw it in the diagram and record each current next to the ammeter in the diagram. c. Use the voltmeter to measure the TOTL potential difference across the circuit and the potential difference across each bulb. Draw the 4 positions of the voltmeter on your diagram, and record the values of the voltage next to the voltmeters in the diagram. Diagram and Patterns for COMBO Circuit
Summarize your findings: Series Current through light bulbs: Parallel Current through light bulbs: Potential difference across light bulbs: Potential 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 potential difference of all elements in a loop. Did you know? Elements in Series: When circuit elements are connected in series, the current through each element is the same and the potential difference across the elements is the sum of the potential differences across each element: I 1 = I 2 = I 3 = I total V 1 + V 2 + V 3 = V total Elements in Parallel: When circuit elements are connected in parallel, the potential difference is the same across each element and the total electric current is the sum of the currents through each element: V 1 = V 2 = V 3 = V total I total = I 1 + I 2 + I 3 2.4 Observe and Explain The readings of three ammeters are shown at the right. What can you say about the magnitude of the current through each of the light bulbs? Explain the pattern.
2.5 Predict (a) For the diagram to the right use analogies and the ideas of potential difference and current to rank the brightness of the bulbs. List the brightest bulb first. Indicate whether any bulbs are equally bright. Explain your ratings. (b) Check your prediction using the PhET Circuit Construction Kit and write your conclusions. 1 2 4 3 2.6 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. 2.7 nswer 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? 2.8 Using the Circuit Construction Kit, determine how connecting two or more batteries in series affects the total potential difference of the circuit. How does this differ from connecting two or more batteries in parallel?