Science Olympiad Circuit Lab: a study guide you can run
- 192parts on the bench
- 25boards running now
- 1.00xreal time, on every board
Circuit Lab is on the Science Olympiad event list for the 2027 season in both Division B (middle school) and Division C (high school). Teams answer questions about electricity and do hands-on tasks, which usually means measuring a real circuit with a multimeter. Most study material online is notes and old PDF tests. Notes are useful, but they cannot give you the feel of reading a meter, and that is the part people lose points on.
This guide is built the other way around. Each topic below is a short explanation followed by a circuit you open in the editor and measure. The circuit above is two sources feeding one node, the kind of Kirchhoff problem that separates teams who can do node analysis from teams who cannot. Press Run and the meter reads the node voltage. Work it out on paper first, then check.
Two things this page will not do. It does not reproduce the Circuit Lab rules, which change every season and belong to Science Olympiad. Read the current rules for your division at soinc.org before you plan your study, because the topic list, the allowed notes and the calculator rules all come from there. And it is not affiliated with Science Olympiad in any way.
Ohm's law and power
Everything else is built on V = I x R and P = V x I. In the Ohm's law circuit, a 9 V bench supply drives a 470 ohm resistor with the meter in series on DC amps. It reads 19.1 mA. Turn the supply up to 12 V and it reads 25.5 mA, which is the same ratio: double-check that 12 / 9 and 25.5 / 19.1 agree before you trust your setup on test day.
Power is where test writers hide the trick. At 9 V that resistor dissipates about 0.17 W, which is more than the 1/8 W rating of a small resistor. A question that asks "what happens to this part" is really asking you to compare those two numbers.
Series and parallel
In series, the current is the same everywhere and the voltages add up to the supply. In parallel, the voltage is the same across every branch and the currents add up. Students who can say those two sentences and apply them without thinking finish the written section with time to spare.
The series-parallel circuit puts both ideas in one place: 10 V into a 1 k resistor, then two 2 k resistors in parallel. The pair is worth 1 k, so it takes half the supply. The meter reads 5.00 V across it. Move the meter into series with one 2 k branch and you read 2.50 mA, which is half of the 5.00 mA through the 1 k.
Kirchhoff's laws
The current law says the currents into a node add up to the currents out of it. The voltage law says the voltages around any closed loop add up to zero. Division C tests like to use two sources, because one source lets you get away with series and parallel shortcuts and two sources do not.
In the circuit at the top of this page, 12 V feeds node A through 1 k and 6 V feeds it through 2 k, with 3 k from A to ground. Node analysis gives 8.18 V, and that is what the meter reads. The interesting part is the 2 k branch: A is higher than 6 V, so current flows backward into the 6 V source, about 1.09 mA of it. Put the meter in series with that branch and the minus sign on the display tells you so.
Capacitors and RC circuits
A capacitor charging through a resistor reaches about 63 percent of the supply after one time constant, tau = R x C, and about 99 percent after five. With 10 k and 100 uF, tau is one second, slow enough to watch.
In the RC circuit the scope shows five seconds across. Flip the switch to charge the capacitor and read the trace: 3.15 V at one second and 4.29 V at two seconds, on a 5 V supply. The scope’s own 1 megohm input takes about 1 percent off both the final voltage and the time constant, which is a real effect on a real bench too.
Diodes and LEDs
A diode conducts one way and drops a roughly fixed voltage while it does. The diode circuit has a 1N4148 silicon diode and a red LED, each behind 330 ohms from 5 V. The meter reads 0.74 V across the silicon diode and 1.65 V across the LED. Turn the diode around and the meter reads the whole 5.00 V across it, because no current flows and nothing else drops any voltage.
Those forward voltages come from each part’s model at that current. A real LED of a different color or brand will read a little differently, which is why a good test question gives you the forward voltage rather than expecting you to know it.
Meters, and what they do to a circuit
A voltmeter goes across a part, an ammeter goes in series, and an ohmmeter only works with the power off. Then there is the question good teams get right: the meter is part of the circuit. Two 10 megohm resistors divide 10 V. A 10 megohm voltmeter across the bottom one reads 3.33 V, not the unloaded 5.00 V. The meter-loading circuit shows exactly that, and with 10 k resistors the same meter reads 5.00 V.
If you only have time for one habit, make it this one: before you read the display, say out loud where each lead is and which jack the red lead is in.
Division B and Division C
Division B students should own the first two sections and the meter section: closed circuits, series against parallel, Ohm’s law and reading a meter. The Division B starter guide covers that ground at a middle school pace. Division C students should expect all six topics and more. Past rules have also included magnetism and the history of the field, which this simulator does not cover. Check this season’s rules for the exact list.
When you are ready to test yourself, the practice test has 30 questions across ten circuits, each answered by measuring. Then practice with a real meter and real parts too: the event’s hands-on tasks are done on real equipment, and nothing replaces having held the probes.
Questions
Is Circuit Lab a Science Olympiad event in 2027?
Yes. Science Olympiad’s 2027 event list includes Circuit Lab in both Division B and Division C. Your state or regional tournament may schedule it differently, so check with your tournament director as well.
Where do I find the official Circuit Lab rules?
At soinc.org, on the rules page for the current season. This guide deliberately does not copy them. Read them first: they decide which topics, notes and calculators are allowed.
Can this replace practicing with a real multimeter?
No. It is a fast, free way to practice the thinking and the measuring habits, and a coach can assign the circuits to a whole team. The hands-on part of the event is on real equipment, so practice on a real meter and breadboard as well.
Is Mokxi affiliated with Science Olympiad?
No. Mokxi is an independent browser simulator. Science Olympiad is named here only to say which event this guide is for.
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