The purpose of this shop project is to become familiar with the voltages and the behavior of a parallel circuit. This will allow you to compare an actual circuit back to the description.
Using the trainer board that contains a service switch, another light switch, two light bulbs and having the tools of a screw driver, some wire with stake-on ends, and a wire cutter/stripper build the circuit shown in figure 18.
Directions:
1. Make sure the power to the board is turned off and the trainer board is unplugged.
2. Connect a black wire to the service switch.
3. Connect the other end of the black wire to the line side (one side) of the switch.
4. Connect a second black wire from the load side (other side) of the switch to the first light bulb.
5. Connect a third black wire from the load side (other side) of the switch to the second light bulb.
6. Connect a white wire from the other side of bulb 1 to neutral.
7. Connect a white wire from the other side of bulb 2 to neutral.
Figure 18 – Parallel Circuit with one switch and two bulbs
8. If this is a school project have your instructor check to make sure it is wired correctly and ask them to initial this step.
9. Plug it in and turn the service switch on, but leave switch 1 off.
10. Use the steps from the prior section on meter usage to check the voltages at the points on the following table.
| Point 1 | Point 2 | Voltage |
| 1 | 2 | |
| 1 | 3 | |
| 1 | 4 | |
| 1 | 5 | |
| 1 | 6 | |
| 1 | 7 | |
| 6 | 7 | |
| 6 | 5 | |
| 6 | 2 | |
| 6 | 1 |
11. Next, turn the switch on and check the voltages at the points in the following table.
| Point 1 | Point 2 | Voltage |
| 1 | 2 | |
| 1 | 3 | |
| 1 | 4 | |
| 1 | 5 | |
| 1 | 6 | |
| 1 | 7 | |
| 6 | 7 | |
| 6 | 5 | |
| 6 | 2 | |
| 6 | 1 |
12. Next, carefully unscrew light bulb 2 and check the voltages at the points in the following table.
| Point 1 | Point 2 | Voltage |
| 1 | 2 | |
| 1 | 3 | |
| 1 | 4 | |
| 1 | 5 | |
| 1 | 6 | |
| 1 | 7 | |
| 6 | 7 | |
| 6 | 5 | |
| 6 | 2 | |
| 6 | 1 |
13. What has changed? Why are the voltages in steps 11 and 12 the same? Explain in the space below.
14. You should now be able to explain the difference between the operation of a series and a parallel circuit. You should also be able to understand why most loads are in parallel circuits. When you are confident you can do this ask your instructor to sign of on this shop project before you disconnect any wires on the boards. Remember your instructor may ask you to explain what you learned.