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techdirections March 2017 : Page 23

circuits that they have to build and test. Examples of these circuits are in Figs. 1–7. I’ve found this approach works well for several reasons: l Using automotive components allows students to work on circuits at normal battery voltages. l They’re using standard auto-motive bulbs and sockets found on modern vehicles. l By mixing in some “bad” bulbs and sockets, students begin trouble-shooting circuit problems quickly. l Circuits, such as that in Fig. 2, tend to generate quite a bit of confu-sion at first but end up as a great example of how voltage drops can really affect a circuit. For this circuit, the students are told the 1157-type of bulb is supposed to work. Students will typically make and test between 10 and 20 different circuits like those shown in Figs. 1–7. The number of circuits depends on the needs of the particular student as some grasp the concepts more quickly than others. Once completed, students then have a pass/fail lab test based on creating, diagramming, and testing a series-parallel circuit. Once a student is able to build, test, and explain the operation of a circuit such as that in Fig. 7, he or she is ready to move on to on-vehicle work. As part of the classroom and lab activities, and to demonstrate how resistance and amperage relate in a lighting circuit, I build a basic bulb circuit and connect a scope. Figures 8 and 9 show a single 194-type bulb with voltage and amperage measure-ments. Quite a bit of discussion about bulbs and circuit operation can take place just from these im-ages. Fig. 5—Series-parallel circuit Battery voltage __________ 1156 or 1157 194 Circuit resistance ___________ voltage drop 1 ___________ voltage drop 2 ___________ voltage drop 3 ___________ 194 voltage drop 4 ______________ ohm’s law predicted amperage ________ Measured amperage _________ 194 194 Fig. 6—Series-parallel circuit Battery voltage __________ Circuit resistance ___________ voltage drop 1 ___________ voltage drop 2 ___________ voltage drop 3 ___________ voltage drop 5 ___________ 1156 or 1157 1156 or 1157 voltage drop 4 ______________ voltage drop 6 ______________ ohm’s law predicted amperage ________ Measured amperage _________ Fig. 7—Series-parallel circuit Battery voltage ___________ Circuit resistance _________ 1156 or 1157 1156 or 1157 194 1156 or 1157 1156 or 1157 voltage drop 1 ____________ voltage drop 2 ____________ voltage drop 4 ____________ voltage drop 6 ____________ voltage drop 3 _____________ voltage drop 5 _____________ voltage drop 7 ____________ ohm’s law predicted amperage ________ Measured amperage _________ Drawings © cengage Learning 2014 Fig. 8 Fig. 9 www.techdirections.com aUtomotive tecHnoLogy 23

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