Physics

How to Test which Solids and Liquids are the best Conductors of Electrical Current



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Testing which solid and liquids are the best conductors of electrical current is easy, and with a little preperation this science experiment can even be done at home. Conductors are materials which electricity can travel through, whereas insulators or resistors are materials or substances which inhibit the flow of electrical current. Being able to test a range of substances to see which are the best electrical conductors makes for a fun and educational science lesson.

- How to test which solids and liquids are the best conductors of electrical current -

For this simple experiment you will need:

- a 6 or 9 volt battery
- 3 lengths of insulated copper wire, around 10 inches long.
- a flashlight bulb, ideally in a socket
- a range of materials to test

To test liquids as well, you will also need some paper clips and a medicine cup.

 - Instructions -

1. For all 3 pieces of wire, remove 1 inch of the insulating coating from each end of the wire. This can be done by using wire strippers, or by carefully scraping the plastic insulation off.

2. Using the 1st piece of wire, wrap the bare end around one of the terminals on the battery. Attach the other end of the same wire to the end of the bulb's socket, or if the bulb is socketless, wrap the bare end of the wire around the bulb's base.

3. Using the 2nd piece of wire, attached one bare end to the other side of the bulb's socket, or wrap around the bulb's base. Leave the other end of this piece of wire free.

4. Using the 3rd piece of wire, attach one bare end of this to the remaining battery terminal, and leave the other end free. This means there is a gap between the 2nd and 3rd pieces of wire. If you touch the two free ends together, the circuit will become complete, and the light bulb will glow brightly.

5. To test whether solids are good conductors of electrical current, touch the free ends of the two wires to the ends of the object. If the material conducts electricity, the light will glow brightly. If the light glows dimly, this means that the material offers some resistance to the electrical current; it conducts electricity but is not as good a conductor as some other materials. If the light does not glow at all, then the material tested is an insulator, and no electrical currently can pass through it.

- Testing liquids -

To test the conductivity of liquids, attach a paper clip to the loose ends of the two wires, and attach the clips to the sides of a medicine cup. Pouring liquid into the cup and seeing whether the bulb lights up, will indicate whether the liquid is a good conductor.

As a side note, whilst testing liquids you might find that the bulb doesn't light but instead bubbles form around the paperclips - this is process of hydrolysis, where the water (H2O) is becoming hydrogen (H2) and oxygen (O2). This means that the liquid is conducting enough electricity to hydolyze the water, but not enough to complete the circuit fully and make the bulb glow.

- Taking notes -

Repeat the experiment above using a range of solids and liquids and keep a note of your findings, based upon which substances make the light glow the brightest e.g. are the best conductors, and which once stop the light coming on altogether. Good materials to test include metal objects, such as forks and different types of nail, plastic, wood, glass, rubber and even fruit! For liquids, try testing water, alcohol, salty solutions and a saturated solution of baking soda, and make a note of the results.

If you want to be a little more precise in your measurements, a battery operated volt-ohm-current meter, available from electronics or hardware stores, can be used in the circuit - once set to measuring ohms, the meter will measure the resistance of each test material within the circuit, and give much more accurate results.

- Sources -

http://www.delta-education.com/downloads/samples_dsm/ElectCircuitsLink1.pdf
http://www.allaboutcircuits.com

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