Prof. Dr. Thorsten Jungmann (last updated 2025-09-03)
1 What does it look like?
The LED torch with solar cell and dynamo (German: LED-Taschenlampe mit Solarzelle und Kurbeldynamo) has a black plastic housing that is closed at the front with a transparent cover. A folding hand crank is mounted on one side. On the opposite side there are solar cells.
2 What can it do?
The torch provides light even in emergencies, for example during a prolonged power cut. The built-in rechargeable battery can be charged by cranking or by sunlight.
3 How does it work?
The crank is connected to a generator via gearwheels (to increase the rotational frequency). The generator produces an alternating voltage, which is rectified by four diodes and fed to the built-in rechargeable battery. The solar cells supply the built-in rechargeable battery with direct voltage and charge it when the sun shines on them. The three white light emitting diodes are connected to the rechargeable battery via series resistors and a switch.
4 What does it look like inside?
- Light emitting diodes
- Switch
- Solar cell
- Generator
- Diodes
- Rechargeable battery
5 What role does it play in teaching?
The torch serves as a demonstration object. You can use it to illustrate the generation of electricity by electromagnetic induction, the photovoltaic effect, the rectification of alternating voltage and the use of light emitting diodes as a lamp.
6 What role does it play in practice?
In (industrial) practice, this torch plays no role. As a household item, it is a sensible part of your emergency equipment.
Symbols
Letter codes in schematics:
- Light emitting diode lamp: E
- Buffer battery, dynamo and solar cell: G
- Switch: S
Calculations
No calculations are carried out for this torch in the fundamentals of electrical engineering.