The dynamo torch is a mechanically powered flashlight. It is considered a green technology since it requires no batteries. It is powered by cranking a handle. The cranking motion turns a dynamo, which is an electric generator. This produces electricity, which turns on the light.
Check out a video of the dynamo torch:
The faster you turn the crank, the brighter the light becomes. This is because you are producing more energy, which makes the light brighter.
This toy demonstrates that energy can be converted from one form into another. You are converting the mechanical energy, provided by turning the crank, into electrical energy which is used to power the light. Electrical generating stations do this as well. They turn large turbines using mechanical energy, which is usually provided by falling water (hydro power) or hot steam pressure. And these turbines then turn generators which produce electricity for use in our homes and businesses.
A dynamo torch, even though it's a toy, works the same as mechanically powered flashlights which are often kept as emergency lights in case of power outages or other emergencies. In case of such an emergency, you want to be able to have a handy light source which is always ready for use. This is particularly useful for vacation homes, cabins, and other remote locations.
As you put the dynamo torch together, have a close look at the mechanism connecting the crank to the dynamo. You will notice that the dynamo (generator) looks like a small electric hobby motor. It is in fact a motor, but one which is operating in reverse. Generators are basically electric motors going in reverse. For an electric motor to run you must supply electrical power, which makes the shaft of the motor turn. To use it as a generator you turn the motor shaft to generate electricity.
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