No prior knowledge needed. We'll build the idea from scratch — what light really is, how a solar cell turns it into electricity, and why standing in the sun beats standing indoors.
Simple goal: point a small solar panel at different kinds of light, measure the electricity that comes out, and prove that light turns into electricity. We'll also find out which light gives the most power.
You don't need semiconductors, chemistry, or scary formulas. Just these two everyday facts.
A beam of light isn't smooth like water. It's actually a stream of tiny packets of energy called photons. Brighter light just means more photons hitting you every second. That's the whole idea.
Electricity is nothing but tiny particles called electrons flowing through a wire. Get electrons moving in one direction and you have current. Push them harder and you have voltage.
So a solar cell has one job: use light-bullets (photons) to knock electrons loose and get them flowing. Light in, electricity out. Everything below is just the details of how.
Drag the scene to look around. Move the sun with the slider and watch the meters. This is the easiest mark to grab in your viva.
Shine a torch straight down onto your hand — you get a small, bright circle. Now tilt the torch sideways — the same light smears into a big, dim oval. The panel is your hand: straight-on light is concentrated, slanted light is spread thin. Fewer photons land on each spot, so less electricity comes out. That's exactly why "Direct Sunlight at a 90° angle" is the winner in our table.
Examiners love this one. Here's how to understand it without any semiconductor theory.
Picture a full row of cinema seats. When one person (an electron) gets up and walks away, they leave behind an empty seat. If the person next to it slides over to fill it, the empty seat appears to move the other way. That travelling empty seat is what we call a hole.
A hole isn't a real object — it's the absence of an electron. But because it's where a negative electron used to be, the spot acts positive. So: electron = the person who left (negative), hole = the empty seat they left behind (acts positive). That's all you need to say.
Read it like a 5-step comic strip. Demo 2 below plays it out live.
The fancy name for this whole light-to-electricity trick is the photovoltaic effect ("photo" = light, "voltaic" = electricity).
Click anywhere on the dark sky to fire your own photon, or slide the brightness up to unleash a stream. Watch each photon knock a blue electron loose (leaving a pink empty-seat hole), then follow the green current dots powering the LED.
Things needed: a mini solar panel (with an LED attached as the load), a digital multimeter (measures voltage and current), connecting wires, a few light sources (sun, flashlight, tube light), and a thick book to make total darkness.
Slide through the five conditions. The numbers, the sum, and the glowing LED all change to match what we recorded.
| # | Condition | Voltage | Current | Power = V × I |
|---|
A solar cell really does turn light into electricity. The output depends on how much light hits it and what angle it comes from. Dim indoor light gives almost nothing (a flashlight managed just 0.24 mW, and a tube light basically 0), while direct sunlight straight-on gave the most (384.75 mW) — over a thousand times more. More light-bullets, hitting straight on, means more electrons knocked loose, means more power.
Tap each question. These are the ones examiners actually ask.
Light is made of tiny energy packets called photons. When they hit the cell, they knock electrons loose. A built-in electric push inside the cell drives those electrons around a wire, and moving electrons are electricity. Light in, current out.
It's the empty space left behind when an electron gets knocked away — like an empty seat in a full row. Since an electron (negative) has left, the empty spot behaves as if it's positive. Holes and electrons move in opposite directions.
Two reasons. First, sunlight has far more photons per second than a distant tube light. Second, indoor light spreads out and gets weaker with distance. Fewer photons means fewer electrons knocked loose, so barely any current flows — that's why the tube light showed almost no power.
Like a torch on your palm: shine it straight down and the light is concentrated; tilt it and the same light smears over a bigger area, so each spot gets less. A panel facing the sun straight-on catches the most photons per area, giving the most electricity.
Because the LED is connected and uses up some of the voltage to glow. What we measure is what's left over after the LED takes its share. The panel on its own, with nothing attached, would read higher.
From nuclear fusion in the sun's core: hydrogen fuses into helium, and a tiny bit of mass is lost. That lost mass becomes a huge amount of energy (Einstein's E = mc²), which reaches us as sunlight — the photons our panel uses.
On the voltage setting it measures the electrical "pressure" pushing the charges. On the current setting it measures how many electrons flow per second. Multiply the two and you get power — the formula P = V × I.