Liquid Resistors

Liquid Resistor Project

Pure water has very
high resistance because
its electrons are tightly
held in place. Impurities
(such as dissolved dirt,
minerals, or salt)
decrease the resistance
because they have
loose electrons, which
disrupt the structure and
make it easier for other electrons to move
through.

Build the circuit, set the meter (M6) to the 0.5mA setting,
and set the slide switch (S5) to position B. Add about 1/4 inch
of water to a cup or bowl. Connect the jumper wires to the
circuit as shown and place the loose ends in the water, make
sure the metal parts aren’t touching each other. Measure the
current through the water.
Add salt to the water and stir to dissolve it. The current
should be higher now, since salt water has less resistance
than plain water. If the current is too high to measure on the
0.5mA scale, switch to the 50mA scale.
Now add more water to the cup and watch the current.
If you have some distilled water, place the jumper wires in
it and measure the current. You should measure close to
zero current, since distilled (pure) water has very high
resistance. Normal water has impurities, which lower its
resistance. Now add salt to the distilled water and watch the
current increase as the salt dissolves!
You can also measure the current through other liquids.
Don’t drink any water or liquids used here.

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