VusumuziMathonsi PS3AFET 200902235Topic: Electricity circuitsTheory: We know that when charges move around a circuit in the same direction atall time, the current is said to be direct current (dc). Batteries produce this kind ofcurrent in electric circuits. Moreover, we also know that circuits come in series wiringor parallel wiring. Series wiring means that the devices are connected in such a waythat there is the same electric current through each device and if the current isinterrupted at one device then it will be interrupted at the other devices too. Parallelwiring means that the devices are connected in such a way that the same voltage isapplied across each device and the current interrupted at any devices does notinterrupt the current at other devices. Lastly, we know that current can be measuredwith a device known as an ammeter. An ammeter is an instrument that measures thecurrent and therefore to be connected to the circuit so that the current can passthrough it.Experiment 1Aim: The aim of the experiment is to observe the brightness of bulbs wired in seriesas we unscrew bulbs from the circuit and as we rewire the circuit to include lessbulbs than there were initially.Hypothesis: I think that when a bulb gets unscrewed the remaining bulbs will notlighten up because when in series current interrupted at one device will interrupt thecurrent at other devices. As for the rewiring of the circuit, I think that if there arefewerbulbs in the circuit then they will shine brighter than if there were more because thevoltage gets divided amongst fewer bulbs.Experiment proceduresApparatus:3 identical bulbs3 sockets2 batteriesWires
VusumuziMathonsi PS3AFET 200902235Precautions:1. Be aware not to break the bulbs and possibly injure yourself.2. Do not choke on any of the components.Method:1. Connect the apparatus to make a series wired circuit as in the figure.2. Switch ON the switch and write your observations.3. Unscrew bulb 1 from the socket and write what you observe.4. Unscrew bulb 3 from the socket and write what you observe.5. Remove bulb 3 from the circuit and then re-wire the circuit so that it includesonly two bulbs and then compare the brightness of the bulbs with when threebulbs were connected.Results:1. When we switched the circuit ON all the bulbs did not shine so we used anextra battery and the bulbs were slightly bright and they were all equallybright. We decided to carry on using two batteries throughout the experiment.2. Upon unscrewing bulb 1, none of the bulbs shone.3. Upon unscrewing bulb 2, the remaining bulb still did not shine.4. When we re-wired the circuit to only include two bulbs we observed that thebulbs shone brighter than when there were three bulbs connected to thecircuit.
VusumuziMathonsi PS3AFET 200902235Discussion:We experienced a slight problem in the experiment with the battery, when we used itthe bulbs did not shine at all. Firstly we thought that maybe our connection of thecircuit was wrong but when we just added an additional battery the bulbs all turnedON but not so brightly though.Furthermore, when we unscrewed the first bulb wewere not surprised by what we observed because we know that by unscrewing thebulb we had just created an open circuit hence the circuit is broken and none of thebulbs will work because they are connected in series. When we re-wired and onlyhad two bulbs, the bulbs shone equally bright, although not so bright, it was brighterthan when there were three bulbs.Conclusion:The circuit is wired in series, meaning that the bulbs are connected in such a waythat the same current passes through all the bulbs. But if a bulb is unscrewed thatmeans that the circuit is incomplete therefore current is not flowing and the otherbulbs will not shine as we observed. Furthermore, the re-wiring of the circuit toinclude only two bulbs should give us two bulbs shinning brighter than they did whenthere were three bulbs and so we observed was the case. This is because thevoltage is divided between the bulbs and this means that the less bulbs there arethen the more voltage they will get and hence they will shine brighter. Therefore myhypothesis is proved to be true.Experiment 2Topic: Electric circuitsAim: The aim of the experiment is to observe the brightness of bulbs wired inparallel as well as an indicator bulb wired in series as we unscrew bulbs from thecircuit. We also want to measure the current in the circuit.Hypothesis: I think that as we unscrew a bulb then the other bulbs will still carry onshining because they are wired in parallel therefore an interrupted current at onebulb will not interrupt the current in the other bulbs. I think the current we measurewill increase with more bulbs we add and decrease with the subtraction of the bulbs.
VusumuziMathonsi PS3AFET 200902235Experimental proceduresApparatus:4 identical bulbs4 sockets2 batteriesWiresConnectorsPrecautions:1. Be aware not to break the bulbs and possibly injure yourself.2. Do not choke on any of the components.Method:1. Construct a circuit as in the figure, where three identical bulbs 1-2- and 3 arein parallel and a 4thbulb is in series and acts as an indicator bulb.2. Switch ON the switch and observe what happens to the bulbs. Do they shineequally?3. Is the indicator bulb the same brightness as the other bulbs?
VusumuziMathonsi PS3AFET 2009022354. Unscrew bulb 1 from the socket and write what you are observing? Will theindicator bulb becomes dimmer or brighter or remain the same in terms ofbrightness? What is the main reason for that?5. Unscrew bulb 1 and 2 from the socket. Observe what happens to bulb threeand the indicator bulb.6. Instead of checking the brightness, connect an ammeter in place of theindicator bulb and measure the current and then comment on the brightnessof the bulbs and the current on the indicator.Results:1. When we switched ON the switch only the indicator bulb shined.2. Therefore the indicator bulb did not have the same brightness as the otherbulbs because the other bulbs did not switch on. I attribute this perhaps to afailure in constructing the circuit correctly or maybe the voltage was notenough to light bulbs 1-2 and 3.3. When we unscrewed bulb 1 from the socket we observed that bulbs 2 and 3turned on but very dim and the indicator was very bright but as compared tobefore the brightness of the indicator bulb was the same and this can beattributed to the fact that because the indicator bulb is in series, any changesto the bulbs in parallel will not affect the voltage passing through the indicatorbulb.4. When we unscrewed both bulb 1 and 2 from their sockets then we observedthat bulb 3 becomes the same brightness as the indicator bulb becauseeffectively the circuit is now wired in series and bulb 3 is actually connected inseries now too.5. When we replaced all the bulbs to their original places as in the beginning andthen replaced the indicator bulb with an ammeter to measure the current, thefollowing was true:Number of bulbs Ammeter measurement(A)Brightness3 0.51 Does not shine2 0.34 Shines, equally1 0.18 Shines very bright
VusumuziMathonsi PS3AFET 200902235Discussion:When the circuit was switched on the beginning with all bulbs connected, only theindicator shined, which surprised me because I thought that the bulbs in parallel;would shine too perhaps not as bright. This led me to believe maybe the voltagefrom the batteries we used were not enough to light the bulbs or maybe our circuitwas not connected correctly. Surprisingly, when we unscrewed bulb 1, the other twobulbs in parallel lit up even though not so brightly. I do not know why this is andperhaps further investigation needs to be done on this occurrence from myexperiment. What was not surprising at all was the fact that bulb three lit up as brightas the indicator bulb when bulb one and two were removed from their socket. This isbecause the circuit had effectively been turned to one that was just wired in seriestherefore the voltage was divided between the two bulbs and that explains why theyshone equally. In respect to the measurements of the current, we observed that themore bulbs there were then the more current we measured and this is because whenbulbs are in parallel each bulb receives current as if the other bulbs were not there.Therefore all the bulbs together draw more current from the battery than does eitherbulb alone. Furthermore, when looked at their brightness we noticed that the morebulbs there were the less bright they were and this is because voltage is dividedbetween the bulbs so if there is only one bulb it will get all the voltage and hence willbe brighter as we have seen in our experiment.Conclusion:As I had mentioned in my hypothesis that I believed that the more bulbs we have thehigher measurement of current we will and the reverse also. The experiment showsthat that is true. We know now that that is because the more bulbs there are theremore current they pull from battery. In regards to the brightness of the bulbs we haveobserved that for the most part if we unscrew a bulb then the other two bulbs inparallel will carry on shining, even brighter than before and equally so. When weunscrewed two bulbs the remaining bulb shined as brightly as the indicator bulbbecause effectively they were connected in series so they shared the voltage.Furthermore, we also identified an error that perhaps could be investigated further inother experiments; when we had all bulbs connected those in parallel did not light
VusumuziMathonsi PS3AFET 200902235until we unscrewed one of those lights then they shined even though very dimly. Forthe most part, my hypothesis turned out to be true except for the errors we couldattribute to incorrect connection of our circuit.
VusumuziMathonsi PS3AFET 200902235Group Members: Student number:1. >2. >Due Date: 14 May 2013PS3AFETPHYSICS FOR FET
VusumuziMathonsi PS3AFET 200902235BibliographyCutnell, J. Johnson, K. (2008). Physics 8thEdition. Southern Illinois: Wiley & Sons,INC.