Solar Cell Experiment for Kids: Light, Angle, Power

Here is the result that surprises almost everyone, including adults. Take a solar panel into bright sun, measure its voltage, then carry it indoors and measure again. The voltage barely drops. Now measure the current instead: indoors it collapses to a few percent of what it was. That single pair of readings is the whole point of a good solar cell experiment for kids, because the story most people carry around, that more light means more voltage, is wrong. More light means more current. Once a kid knows which number moves, they can reason about rooftops, calculators, satellites and the odd fact that a hot panel performs worse than a cold one.

Key Takeaways

• You’ll measure open-circuit voltage and short-circuit current from a hobby solar panel under different brightness levels and tilt angles, then plot current against angle.
• It teaches the photovoltaic effect, the cosine law for tilted surfaces, and why partial shade ruins a whole panel.
• Best fit is ages 9 to 15. A multimeter is what makes this an experiment rather than a toy.
• The usual failure is a cheap panel that cannot drive a motor at all. Measure current with the meter first; don’t judge the panel by whether the motor spins.
• No mains electricity, ever. A solar panel is a battery-class source and must never be connected to anything that plugs into a wall.

What You’ll Need for This Solar Cell Experiment for Kids

Item	How much	Where to get it	If you don’t have it
Small solar panel, 2–6 V, 100 mA or more	1	Hobby or electronics shop, $4–10	Break open a cheap garden stake light; the panel inside is usually 2 V
Multimeter with a mA range	1	Hardware shop, ~$12	Nothing substitutes properly; borrow one
Alligator-clip leads	2	Electronics shop	Twisted bare wire
Small DC motor or a 2 V LED	1	Dead toy, hobby shop	A buzzer works and is louder
Protractor and a stiff card	1	School supplies	Print an angle template and fold the card to match
Tape measure	1	Kitchen drawer	A ruler and a bit of patience
Desk lamp	1	Anywhere in the house	Direct sun; just keep conditions steady
Graph paper or a spreadsheet	1 sheet	Printer	Plain paper and a ruler
Index card for shading	1	School supplies	Any opaque scrap

Time: prep 10 min, experiment 40 min, cleanup 2 min Cost: $15–25 if you buy the panel and meter, under $5 if you harvest a garden light Mess level: low

Do the Experiment

Step 1 — Measure voltage in bright and dim light

Set the meter to DC volts. Clip it across the panel with nothing else connected. Record the reading in direct sun or under the lamp at 10 cm, then walk it into a dim room and record again.

What you should see: a drop, but a small one. A panel reading 2.1 V in sunlight might read 1.8 V in room light. That’s open-circuit voltage, and it depends on the light level only weakly.

Step 2 — Now measure current the same way

Move the meter to the mA range and put it directly across the panel, which measures short-circuit current. Repeat the bright and dim readings.

What you should see: a collapse. A panel giving 120 mA in sun may give 3 mA in room light, a 40-fold change over the same conditions that barely moved the voltage. Write both pairs of numbers side by side; this contrast is the experiment.

Step 3 — Vary distance from the lamp and record current

Keep the panel flat and facing the lamp. Measure current at 10, 20, 30, 40 and 60 cm. Keep the room otherwise dark so the lamp is the only source.

What you should see: current falls fast, roughly as one over distance squared once you are a few lamp-widths away. Doubling the distance cuts the current to about a quarter.

Step 4 — Tilt the panel through known angles

Back to a fixed distance. Use the protractor and card to hold the panel at 0°, 15°, 30°, 45°, 60° and 75° away from facing the light squarely. Record current at each angle.

What you should see: current follows the cosine of the angle closely. At 60° you should get roughly half of the 0° value, because cos 60° = 0.5. Plot current against angle and the shape is unmistakable.

Step 5 — Shade one strip and watch everything stop

Look closely at the panel: most are divided into several narrow cells wired in series. Cover just one of those strips with the index card, leaving the rest in full light.

What you should see: output falls far more than the fraction you covered. Shading a quarter of a panel can take most of its current away, because the cells are in series and the darkest one throttles the whole chain. This is why a single branch shadow matters so much on a real roof.

Step 6 — Connect a load and work out watts

Clip the motor across the panel in full light. With the meter in series, read the current; then move the meter to read voltage across the motor while it runs. Multiply the two.

What you should see: both numbers are lower than the open-circuit voltage and the short-circuit current you measured earlier. That’s normal and important: a panel delivers its maximum power somewhere between those two extremes, not at either one.

What’s Actually Going On

A solar cell is a large, thin semiconductor diode. In silicon, a photon carrying more than about 1.12 electronvolts of energy, which means any wavelength shorter than roughly 1,100 nanometres, can knock an electron out of a bond and leave a positively charged hole behind. The cell has a built-in electric field at the junction between its differently doped layers, and that field sweeps electrons one way and holes the other. Connect a wire and you have current. The US Department of Energy’s photovoltaics overview describes the same mechanism for modules rather than single cells.

Now the two numbers you measured. Short-circuit current is set almost entirely by how many usable photons arrive per second, so it is nearly proportional to irradiance. Open-circuit voltage is set by the junction itself and depends on light only logarithmically, which is why it hardly budged. A silicon cell gives roughly 0.5 to 0.6 V in sunlight no matter whether that sunlight is bright or merely adequate. Your 2 V panel is four cells in series.

The cosine result in Step 4 is not about the cell at all. It is geometry. A tilted panel intercepts a beam across a projected area of A·cos θ, so the power landing on it falls off as the cosine of the angle away from square-on. PVEducation’s treatment of solar radiation on a tilted surface sets out the full version, including why fixed rooftop arrays are usually tilted near the site’s latitude.

Two popular claims are worth correcting. First, panels do not need heat; they need photons. Cell voltage falls as temperature rises, by roughly 0.3 to 0.45 per cent of output per degree Celsius for silicon, so a panel baking at 65 °C produces measurably less than the same panel at 25 °C in the same light. The DOE’s performance and efficiency page explains why module ratings are quoted at a standard 1,000 W/m² and 25 °C. Second, nobody is hiding a 90-per-cent-efficient panel. Shockley and Queisser worked out in 1961 that a single-junction cell in sunlight cannot exceed about 33 per cent, because photons below the bandgap pass straight through and the excess energy of high-energy photons turns into heat. Commercial silicon modules reach the low twenties. That gap between 23 and 33 is engineering; the gap between 33 and 100 is physics.

How to Explain It to Your Kid

Ages 5–8: Light is the food

The panel eats light and turns it into push. Hold the panel up to the window and let them hear the motor speed up. Then put your hand over part of it and let them hear it slow. Let them chase the brightest spot in the room with the motor running; the sound becomes a light meter they can hear.

The useful question for this age is not how it works but where it works. Walk around the house with the motor buzzing: by the window, in the hallway, under the lamp, in the fridge with the door open. They will find the pattern themselves.

Ages 9–12: Two different numbers

Introduce volts as “how hard the push is” and amps as “how much is flowing.” Then show them their own table from Steps 1 and 2 and ask which column changed when the light changed. Almost every kid predicts voltage. The table says current. That moment of being wrong on paper is worth more than a correct guess would have been.

Then give them cos 60° = 0.5 and let them check their own angle data against it. For another way into the same energy budget, our write-up of how solar panels work fills in the module side.

Ages 13+: Find the maximum power point

Give them the full picture: a cell is a current source in parallel with a diode, so its current-voltage curve is flat at low voltage and then rolls over. The product of V and I is zero at both ends and peaks in between, at what engineers call the maximum power point. The extension that makes this a real investigation: wire a potentiometer or a set of fixed resistors as the load, record V and I for each, and plot both the I-V curve and the power curve. The peak you find is the number a real inverter spends its whole life chasing. Pair it with a solar oven you can measure to compare photovoltaic and thermal collection from the same sunlight.

The question to ask: “If we put two of these panels side by side, which number doubles: the volts or the amps? What if we stack them end to end instead?”

Why Teaching This Early Pays Off

The distinction between voltage and current is the single most useful idea in elementary electricity, and it is also the one that school tends to teach as a formula rather than an observation. A kid who has watched one number hold steady while the other collapsed has a grip on it that a definition does not provide. The same reasoning turns up later in batteries, in chargers, in why a USB cable has a current rating, and in any conversation about grid-scale renewables.

The cosine result pays off twice: once in trigonometry, where students usually meet cosine as an abstraction, and again in earth science, where the cosine of the solar angle is the actual reason seasons exist. Having measured it with a panel, “the sun is lower in winter so the same beam spreads over more ground” stops being a sentence to memorise.

One afternoon does not change a trajectory, and it would be dishonest to suggest otherwise. What the research does support is narrower: Chi and Wylie’s ICAP framework ranks learning by how actively the learner engages, with constructing explanations and arguing about them beating both doing and watching. So the plotting and the arguing about why voltage didn’t move are where the value sits, not in the panel itself. The National Research Council’s K-12 framework names analysing and interpreting data as one of eight core science practices, and that is precisely what Step 4 is.

Before You Start: What Parents Should Know

Best age	9 and up for the measurement work. Ages 5 to 8 get real value from the motor-and-window version without any numbers.
Supervision	Light. The main adult job is keeping the lamp distance consistent and stopping anyone staring at the sun to check it’s bright.
Real hazards	None beyond normal care. A hot desk-lamp bulb will burn fingers. Do not look directly at the sun at any point, and do not use a magnifying lens to concentrate sunlight on the panel: it can scorch the encapsulant and start a fire.
Don’t	Don’t connect the panel to anything mains-powered, and don’t wire it into a household circuit, a USB port or a phone. Don’t use a cracked panel from a broken garden light; the exposed cell edges are sharp and will cut.

When It Doesn’t Work

• The motor won’t turn even in full sun. Most hobby motors need more current than a small panel can supply. Check with the meter: if you read current but get no rotation, the panel is fine and the motor is simply too thirsty. Try an LED, or give the motor a flick to break static friction.
• Current readings jump around indoors. Mains-powered lamps flicker at twice the supply frequency, and some LED bulbs flicker badly. Use sunlight for the angle experiment, or an incandescent bulb, which has enough thermal lag to stay steady.
• The cosine curve looks wrong at steep angles. Reflected light from a wall or a white tabletop is reaching the panel. Put a dark cloth behind and beneath the setup and repeat.
• Voltage reads fine, current reads zero. The meter’s current jack is a separate socket on most multimeters, and its internal fuse blows easily. Move the red lead and check the fuse.
• Sun readings drift during the session. Thin cloud changes irradiance by a factor of several within a minute. Take a reference reading at 0° before and after each measurement and discard runs where the reference shifted.

Take It Further

One variable, one graph. Fix everything except angle, record current at 5° steps from 0° to 85°, and plot both your measured current and the cosine curve on the same axes. Where they diverge is interesting: near 80° the glass surface starts reflecting rather than transmitting, and your data will show it.

Track a real day. Tape the panel flat on a windowsill, read short-circuit current every 30 minutes from morning to evening, and plot it. Then repeat with the panel tilted to your latitude and compare the areas under the two curves. That comparison is the actual engineering decision behind every fixed solar array.

Temperature, deliberately. Take two identical readings in the same light, one with the panel at room temperature and one after it has sat in the sun for 20 minutes with a thermometer taped to its back. Record both temperature and current. The effect is small and real, and finding it takes genuine care.

What to Watch For Over the Next 3 Months

• Week 4: they notice the solar panel on a parking meter, a road sign or a calculator and ask how big it needs to be.
• Month 2: the voltage-versus-current distinction shows up somewhere else, often in a question about why a power bank is labelled in milliamp-hours.
• Month 3: they predict the effect of shade or angle before testing, and they talk about the sun’s height rather than the sun’s strength when explaining seasons.

Frequently Asked Questions

Which panel should I buy for this?

Anything rated 2 V or more and at least 100 mA. Bigger is easier to read but no more instructive. A 5 V, 1 W panel sold for hobby robotics is ideal and costs under $10. Avoid the tiny calculator-sized cells; their currents are too small to show the angle effect clearly.

Do we need real sunlight?

For the brightness comparison, yes, because no household lamp comes close to 1,000 W/m². For the angle and distance experiments a desk lamp is actually better, since it holds still while the sun does not.

Why does my panel work behind glass but not as well?

Window glass absorbs and reflects part of the spectrum, and most domestic glazing has a coating that blocks some infrared. Expect a drop of 10 to 20 per cent. Measure it: that’s a clean, quick experiment of its own.

My kid asked whether solar panels work on the moon. Do they?

Better than on Earth, actually, because there is no atmosphere to absorb or scatter the light. The catch is temperature and dust, not sunlight. It is a good question and worth taking seriously rather than deflecting.

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About the author

Ricky Flores is the founder of HiWave Makers and an electrical engineer with 15+ years of experience building consumer technology at Apple, Samsung, and Texas Instruments. He writes about how kids learn to build, think, and create in a tech-saturated world. Read more at hiwavemakers.com.

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Sources

1. U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy. “Photovoltaics.” https://www.energy.gov/eere/solar/photovoltaics
2. U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy. “Solar Photovoltaic Performance and Efficiency Basics.” https://www.energy.gov/eere/solar/solar-performance-and-efficiency
3. PVEducation. “Solar Radiation on a Tilted Surface.” PVCDROM. https://www.pveducation.org/pvcdrom/properties-of-sunlight/solar-radiation-on-a-tilted-surface
4. PVEducation. “Air Mass.” PVCDROM. https://www.pveducation.org/pvcdrom/properties-of-sunlight/air-mass
5. Shockley, W., & Queisser, H. J. (1961). “Detailed balance limit of efficiency of p-n junction solar cells.” Journal of Applied Physics, 32(3), 510–519. doi:10.1063/1.1736034
6. Chi, M. T. H., & Wylie, R. (2014). “The ICAP framework: Linking cognitive engagement to active learning outcomes.” Educational Psychologist, 49(4), 219–243. doi:10.1080/00461520.2014.965823
7. National Research Council. (2012). A Framework for K-12 Science Education. National Academies Press. doi:10.17226/13165
8. U.S. Energy Information Administration. “Solar explained.” https://www.eia.gov/energyexplained/solar/