In ohms what is the electrical resistance of water?

Answer 1

To figure the resistance of a substance in ohms, more information would be needed. Resistance is calculated by (resistivity)*(length)/(cross sectional area).

First consider a wire conductor. Electrical resistivity is a property of the substance (it usually will vary with temperature). The thicker a wire is (larger cross sectional area) will lower the resistance. The longer the wire will increase the resistance. Now consider water. There is no 'wire' so the cross sectional area of whatever conductor is in contact with the wire will be a factor. A second conductor will need to be in contact with the water to complete the current path. The distance between the conductors is the length. Resistivity has a unit of ohms*meters; when divided by area and multiplied by length, the resulting unit is ohms. The reciprocal of resistivity is conductivity, which has units of Siemens/meter (Siemens is equivalent to 1/Ohms) I have posted a link to the Wikipedia article, listing conductivity values for several conducting elements (and water as well).

Pure water with no impurities actually has a very high resistivity (low conductivity, which means not much current will flow). Pure water is not very common, and the type and amount of impurities affects the conductivity of the water sample.

Conductivity of typical drinking water is in the range: 0.0005 to 0.05 Siemens per meter, so the reciprocal (resistivity) is 2000 Ohm*meters to 20 Ohm*meters. Note from the same chart that deionized water has a conductivity of 5.5 × 10-6 Siemens/meter --> resistivity = 181,818 ohm*meters.