Light > Electricity > Light
The transformation of one form of Energy to another is one of the core ideas of A Child's Physics. is another. The change from Light to Electricity and back to Light can be presented simply and elegantly .
A solar cell and an LED present one of the first transformations. Hobby level solar cells are readily available and inexpensive. An LED can be inserted directly into a low power cell without the need of additional circuit components.
The child can use her knowledge of shadows, the shadow of her hand or a piece of paper, as a control device dimming or stopping the LED putting her in the circuit as a switch. This requires dexterity similar to the combination of laser and mirror. One can also experiment with filters. The device can be carried around the environment producing different results in different areas. A window will not give the same result as the cabinet under the sink. This device presents one of the first examples of Enhanced Measurement. It is a non-quantifying Light sensor. |
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It is necessary to make clear that the solar cell is producing electricity first and then lighting the diode rather than producing light directly. So we also use the cell to drive a motor and a meter, which are taken from the Snap Circuit set presented in the section on Electricity.
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Light can provide power, but it can also provide control.
Light can be used as a switch turning a power supply on and off.
In this case a light sensitive diode
Light can be used as a switch turning a power supply on and off.
In this case a light sensitive diode
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Measurement
The first step in measurement is awareness of the energy to be measured.
The second is to handle a device which is sensitive to that energy.
The third step is to associate quantity, numbers, with that energy.
It is not important in the concrete, sensory stage to understand the definition of the units. The idea is to realize that the energy can in some way be counted, the way one can count ounces and inches. This quickly leads to perception of relative amounts. Here, for instance, the light is more, has bigger number, than somewhere else.
Preference should be given to an analogue display rather than digital. A needle and dial keep all numbers visible and the needle moves. Mechanical motion is more interesting and informative than changing numbers. Because the child has experienced a solar cell the sensor on the top of the meter can be explained. Because the child has used a solar powered motor idea that the sensor produces electricity which drives the needle much like a motor.
The first step in measurement is awareness of the energy to be measured.
The second is to handle a device which is sensitive to that energy.
The third step is to associate quantity, numbers, with that energy.
It is not important in the concrete, sensory stage to understand the definition of the units. The idea is to realize that the energy can in some way be counted, the way one can count ounces and inches. This quickly leads to perception of relative amounts. Here, for instance, the light is more, has bigger number, than somewhere else.
Preference should be given to an analogue display rather than digital. A needle and dial keep all numbers visible and the needle moves. Mechanical motion is more interesting and informative than changing numbers. Because the child has experienced a solar cell the sensor on the top of the meter can be explained. Because the child has used a solar powered motor idea that the sensor produces electricity which drives the needle much like a motor.