Source: https://mokxi.com/learn/tsa-electrical-applications-practice Updated: 2026-09-27 Learn # TSA Electrical Applications: practice circuits for middle school Written by the Mokxi team, updated September 27, 2026 Sign up free or see every lesson - 192 parts on the bench - 25 boards running now - 1.00x real time, on every board Hold the button Two switches in series light the green lamp (AND); two in parallel light the red lamp (OR). Electrical Applications is a middle school event from the Technology Student Association (TSA). TSA describes it this way: students take a test on basic electrical and electronic theory, and semifinalists build a circuit from a schematic, make electrical measurements and explain their solution in an interview. The official rules are in TSA’s middle school competitive events guide, which your advisor has. This page does not reproduce them and is not affiliated with TSA. What follows is original practice for the three skills in that description: building from a schematic, measuring, and explaining. Every circuit opens in your browser, so a whole chapter can practice on school Chromebooks. ## Build from a schematic A schematic shows what connects to what, not where parts sit. Read it one net at a time: pick a point, find everything connected to it, and wire all of those together before moving on. Then check each net with the continuity range on your meter. Practice: open a blank project and build the divider in the linked circuit from this description, without looking at it. Three 10 k resistors in series from 5 V to ground, with a meter across the bottom one. Then open the linked circuit and compare. Your meter should read about 1.67 V. ## Logic with switches: AND and OR Switches in series act like AND: every switch must be on for current to flow. Switches in parallel act like OR: any one switch is enough. Open the switch logic circuit. On the left, switches A and B are in series with the green lamp. On the right, C and D are in parallel feeding the red lamp. Predict each lamp for all four combinations of its two switches, write it as a table, then check. The green lamp lights only for A and B together; the red lamp lights for C, for D, or for both. ## A three-way switch A hallway light that you can turn on or off from either end uses two single-pole, double-throw switches joined by two wires called travelers. Flip either switch and the light changes state, whatever the other one is doing. In the circuit, both switches start toward pin 1, which connects them through the first traveler, so the lamp is on. Flip either one and it goes off; flip the other and it comes back on. Draw the current path for all four switch positions. This is a low-voltage model. Real three-way switches run on 120 V house wiring, which is a job for a licensed electrician, not a student project. ## Measure and record In the series practice circuit, 12 V drives 1 k, 2.2 k and 3.3 k in series. Measure the voltage across each resistor and write the three readings in a table with units. They should come to 1.85 V, 4.06 V and 6.09 V, and they add up to the 12 V supply, which is Kirchhoff’s voltage law and a quick way to check your own work. Good habits that show in an interview: write the unit with every number, say which points you measured between, and check that your readings make sense together before you move on. ## Explain your solution Practice answering these out loud in under a minute each: Why are switches in series like AND? What would happen to the other lamps if one burned out in the series circuit? How did you know your meter was connected correctly? What would you check first if your circuit did not work? Clear answers use the words current, voltage and loop, and they point to a reading you took. That is what a judge is listening for. ## Practice for the written test The test is on basic electrical and electronic theory, so the same few ideas come back again and again: Ohm’s law, power, series and parallel rules, units and prefixes, and schematic symbols. Know each one well enough to use it without a formula sheet. Try these, then check the answers. A 9 V battery drives a 450 ohm resistor: what current flows, and how much power does the resistor turn into heat? Two 100 ohm resistors are wired in parallel: what is the total resistance? A 60 W lamp runs on 120 V: what current does it draw? How many ohms is 4.7 k, and how many amps is 20 mA? Answers: 20 mA and 0.18 W (P = V x I). 50 ohms, since two equal resistors in parallel give half of one. 0.5 A (I = P / V). 4,700 ohms and 0.020 A. If any of those took more than a minute, that is the topic to practice next. ## Practicing as a team Decide who does what before the clock starts. One person can read the schematic out loud, net by net, while the other wires; then swap roles and have the builder check every net with the meter. Saying each connection out loud catches the wire that goes one row off. In the interview, both of you should be able to explain the circuit. Practice by having each partner explain the other one’s part. ## Questions Is Electrical Applications a middle school or high school TSA event? TSA lists it as a middle school event. Check the current competitive events guide with your advisor for the rules and team size. What should we practice on real parts? The build itself. Wiring a breadboard by hand, reading resistor color bands and holding meter probes steady all take practice with real parts, so save some chapter meetings for a real bench. Can we practice on Chromebooks? Yes. Everything here runs in a browser tab with nothing to install, and a teacher can assign the circuits to a class. Related ## Keep going Circuit Lab Division B: Middle School Starter Guide How to Use a Multimeter: Practice on a Virtual One SkillsUSA Electronics Technology Practice Circuits Logic Gates, and the Truth Table You Can Press TSA competitions ## Build this for real Open the editor, change a value and watch the number move with it. Nothing to install, and no account needed. Start building Open the editor