Electricity
The water pushes through the pipe and turns the wheel.
Water
Changing the height or filling the tank adds water and lifts it. That supplies the energy.
Calculations and explanation
Pressure, flow and power
A higher water surface gives more pressure at the pipe. A wider opening lets more water pass each second. The wheel receives energy from the falling water. Water stays in the lower tray; energy does not return to the upper tank.
| Water | Electricity |
|---|---|
| Pressure difference · kPa | Voltage difference · V |
| Litres passing each second · L/s | Charge passing each second · A = coulombs/s |
| Pressure × flow · W | Voltage × current · W |
| Pipe restriction | Electrical resistance |
| Wheel transfers energy | Bulb transfers energy into light and heat |
The paired numbers use 1 kPa ↔ 1 V and 1 L/s ↔ 1 A as a teaching scale. These are different physical quantities, not a conversion of water into electricity.
Pressure = ρgh, with fresh water density 1,000 kg/m³ and g = 9.80665 m/s². Hydraulic power = pressure difference × volume flow. This ideal linear pipe model uses Q = pressure ÷ hydraulic resistance. The wheel turns 65% of hydraulic power into shaft power; the remainder becomes turbulence and heat. Pipe inertia and water hammer are omitted.
A wider tank at the same height gives the same initial pressure. It holds more water and drains more slowly. Moving its width or height controls supplies or removes water externally.
The water picture explains steady current. AC reverses direction repeatedly; it is available in the Electricity example. Real electric circuits need a complete path. Charge is already present in the wires and is not used up by a bulb.