UNIT 7 - DIRECT CURRENT CIRCUITS: CURRENTSTUDIO Unit 07 PHY 2054 – College Physics II[UNIT 07 DIRECT CURRENT CIRCUITS -II: OHM]1 | P a g eUNIT 7 - DIRECT CURRENT CIRCUITS: CURRENT(from Lillian C. McDermott and the Physics Education Group, Physics by Inquiry Volume II, John Wileyand Sons, NY, 1996)Objectives- to understand qualitatively current flow through circuit elements connected in series and parallel- to understand qualitatively the total resistance of networks of bulbs in series and parallel - to understand qualitatively the inverse relationship of current and resistance for networks of bulbs in series and parallel for constant potential difference- to understand independent and dependent networks of bulbs connected in series or in parallel - to understand the concept of open circuits- to understand the concept of short circuitsEquipment:1 short piece of nichrome wire1 battery 1.1 Connect a short piece of nichrome wire (looks silvery and is relatively stiff) across theterminals of the battery. Feel the wire. Does the wire seem to be the same temperatureacross the entire length or are some sections warmer than others? Do a blind test—havesomeone hold the battery while a second person with their eyes closed touches the wire atdifferent places. What does this observation suggest about the amount of current (chargeper unit time flowing) in the wire at one point compared to another point. NOTE: DO NOT KEEP THE WIRE IN CONTACT WITH THE BATTERY FORTOO LONG BECAUSE IT WILL LOSE POWER FAIRLY QUICKLY.Be prepared to discuss your observation with an instructor.Equipment:6 wires with alligator clips3 bulbs3 sockets2 batteries2 battery holdersREMINDER: In these experiments you will be asked to make predictions beforedeciding on a result or measuring it. It is important that you do this because the thinkingthat goes into your decision will allow you to grasp the concepts. Predict THEN verify –PLEASE!!2.1 2 | P a g ea. Predict the brightness of the bulbs in the two-bulb circuit shown below compared tothe brightness of a bulb in a single-bulb circuit. Will the bulbs in the two-bulb circuithave the same brightness? Will the bulbs in the two-bulb circuit be brighter, dimmer orequally bright compared to a bulb in a single bulb circuit? b. Set up a two-bulb circuit and test your predictions. Based on your observations, whatcan you conclude about the amount of current through each bulb in the two-bulb circuit?3 | P a g ec. How does the amount of current through a two-bulb circuit compare to the amount ofcurrent through a single-bulb circuit?d. Do you think it is appropriate to think about charge flowing (current) through thebattery? Explain your reasoning.Be prepared to discuss your answers with an instructor or with the class if there is agroup discussion.e. How does the current through the battery in the two-bulb circuit in part a compare tothe current through the battery in a single-bulb circuit? Explain your reasoning.4 | P a g eDiscuss your reasoning with an instructor.Two bulbs connected as shown in part a are said to be connected in series. The two bulbs in the diagram on the right are said to be in SERIES._______________Equipment:6 wires with alligator clips3 bulbs3 sockets2 batteries2 battery holders5 | P a g e3.1a. Predict the brightness of the bulbs in the two-bulb circuit shown below compared tothe brightness of a bulb in a single-bulb circuit. Will the bulbs in the two-bulb circuithave the same brightness? Will the bulbs in the two-bulb circuit be brighter, dimmer orequally bright compared to a bulb in a single bulb circuit? b. Set up a two-bulb circuit and test your predictions. Based on your observations, whatcan you conclude about the amount of current through each bulb in the two-bulb circuit?c. IMPORTANT: How does the current through the battery in the two-bulb circuitcompare to the current through the battery in a single-bulb circuit? Explain yourreasoning.6 | P a g eBe prepared to discuss your answers.Two bulbs connected as shown in part a are said to be connected in parallel.The Two bulbs in the circuit to the right in this diagram are said to be in PARALLEL.Equipment:9 wires with alligator clips4 bulbs4 sockets2 batteries2 battery holders4.1a. Predict the brightness of the bulbs in a circuit with three bulbs in series compared to asingle bulb circuit and compared to the bulbs in a circuit with two bulbs connected inseries.b. Set up the circuits in part a and test your predictions. What did you observe?7 | P a g ec. Suppose you have a closed box in a circuit as shown below. You observe a brightnessin bulb A. Imagine someone then makes a change in the electrical elements inside thebox. You do not see what has been done. However, you observe that the indicator bulbbecomes brighter. What can you conclude about the current through the battery? d. Suppose you observe that the indicator bulb becomes dimmer. What can you concludeabout the current through the battery? Explain how bulb A is serving as an indicator bulbin this circuit.We can think of a bulb as presenting an obstacle or resistance to the current in the circuit.e. When bulbs are added to a circuit in series, as in part a, does the total resistance of thecircuit increase, decrease, or remain the same? Does the current through the circuit,increase, decrease, or remain the same? How are the current and resistance related forelectrical elements in series? Explain.8 | P a g e4.2 a. Set up a circuit with two bulbs in series, as shown in the diagram below. Consider bulb A to be an indicator bulb. Consider another bulb added to the circuit inparallel to bulb B, as shown in the diagram below. Predict whether the current throughbulb A, the indicator bulb, will increase, decrease or remain the same. b. Test your prediction. How does the brightness of bulb A change when a bulb is addedin parallel to bulb B? How does the current through bulb A change when a bulb is addedin parallel to bulb B? How does the current through the battery change when a bulb isadded in parallel to bulb B? Explain.c. How does the total “resistance” of the circuit change when a bulb is added in parallelto bulb B? How does this change in the resistance of the circuit affect the total currentthrough the battery? 9 | P a g ed. Summarize how the total resistance of a circuit changes(i) when bulbs are added in series(ii) when bulbs are added in parallel Class discussion