Electrical circuits make interesting science projects. They can be very basic, involving only a few elements, or more complicated and ambitious. Electrical circuits can be used to explore different aspects of science such as electromagnetism, the generation of power, solar energy and electrochemistry. You can build your circuits from scratch using separate elements, or you can find electrical circuit kits that you can put together in different ways.
Basic Electrical Circuit
A basic electrical circuit consists of a power source, usually a low-voltage battery; conductive wires; and something to show that current is flowing, such as a flashlight bulb in a holder. One conductor is attached to one terminal of the battery, the other conductor to the other terminal. The ends of the conductors are attached to the terminals of the bulb holder. Using a paper clip and two thumbtacks stuck in a piece of corrugated cardboard, you can make a simple switch to turn the current on and off.
Fruit and Vegetable Batteries
You can use lemons, potatoes and other fruits or vegetables to generate small amounts of electric current. You will need two metal electrodes. A copper coin and a strip of zinc are commonly used: the greater the surface area of the electrode, the better. The acidic juice inside the lemon forms an electrolyte --- a liquid through which electricity can pass. Electrons move from one electrode to the other, producing a current. To make a circuit, you'll need to attach wires to the electrodes. Use the current from the lemon battery to power an electrical device; you can use a flashlight bulb for this, but since the current may be too small to light it, a small clock with an LCD display might be better. Connect several fruit or vegetable batteries together for a larger current.
A basic electromagnet is easy to build. Simply take a piece of ferrous metal, such as an iron nail, and wrap wire around it in coils. When you connect the ends of the wire to a power supply, such as a battery, the coiled wire induces an electromagnetic field in the metal core and it becomes a temporary magnet. The more coils, the stronger the magnet.
You can build your own direct current electric motor very easily. You'll need a permanent magnet, a battery, some copper wire, and two angled pieces of conductive metal with holes punched in them large enough for the wire to pass through easily. You'll need to make a coil of wire with the two ends sticking out from it. Set the angled strips of metal like bookends with the wire coil positioned in the middle so it hangs over the permanent magnet. Connect each of the battery terminals to one of the strips of metal. You should see the coil of wire spin around, as the electromagnetic field induced within the coils is repelled by the permanent magnet.
You can obtain photovoltaic cells and small solar panels very cheaply. These can be used to power a number of devices, such as an electric radio. You can also use solar panels in experiments to demonstrate how the angle of the sun affects the amount of light falling on the panel, or how the current produced by the panel varies with the intensity of the light falling on it.
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