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Give and Take: Can an Electric Current Move Through Water?

based on 11 ratings
Author: Janice VanCleave

Problem

Can an electric current move through water?

Materials

  • duct tape
  • 3 size D batteries
  • 1/2 cup (125 ml) of distilled water
  • cereal bowl (very clean)
  • 12-inch (30-inch) aluminum foil strip
  • 2 clothespins
  • size D (11/2-volt) flashlight bulb
  • 2 helpers (one must be an adult)

Procedure

WARNING: Electricity can be dangerous. Use only 1/2-volt batteries—and do not use more than three batteries.

  1. Tape the three batteries together with positive terminals touching negative terminals.
  2. Pour the distilled water into the bowl.
  3. Stand the flat, negative terminal of the battery column in the bowl of water. Ask your adult helper to support the column.
  4. Lay one end of the foil strip under the surface of the water in the bowl so that it is near, but not touching, the column of batteries. Hold the strip in position by clipping it to the side of the bowl with a clothespin.
  5. Tightly wrap the free end of the foil strip around the metal base of the flashlight bulb. Secure with a clothespin.
  6. Squeeze the clothespin tightly against the base of the bulb while pressing the bulb's metal bottom against the raised, positive terminal of the battery column.
  7. Ask a second helper to darken the room by closing the window shades and turning off the light
  8. Observe the bulb for about 5 seconds.

WARNING: While the procedure in this experiment is safe, you should not touch this, or any, solution that is connected to an electric current.

Results

The bulb does not glow.

Give and Take

Why?

The flashlight bulb glows only when an electric current flows through its filament In a circuit, the negative terminal of the connected batteries repels electrons and the positive terminal attracts them, producing a flow of electric charge. However, for electric charges to flow, there must be a closed circuit which is an unbroken path connecting the bulb and the batteries. Distilled water is not a conductor, so the electric current is interrupted; thus, the bulb does not glow.

WARNING: While it is true that distilled water does not conduct electricity, most water is not distilled so you should never place any electrical appliances in water.

Let's Explore

  1.  
    1. How would adding an electrolyte to the water affect the results? Repeat the experiment by adding 2 teaspoons (10 ml) of table salt to the water in the bowl, and stir until the salt is dissolved. Table salt, like all electrolytes, conducts an electric current when mixed with water. The brightness of the bulb indicates the strength of the current. A large current produces the brightest light. NOTE: If the bulb does not glow, make sure the foil is wrapped tightly around the bulb and ask your adult helper to press the connected batteries firmly together.
    2. Test other substances to determine whether they are electrolytes or nonelectrolytes. Repeat the previous procedure twice, starting with fresh distilled water in a clean bowl each time. First replace the salt with sugar and then with baking soda. Science Fair Hint: Photographs showing the steps of the procedure can be used as part of a project display.
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