Electrons move through a conductor when electric current flows. All material impede flow of electric current to some extend. Some materials hold their electrons very tightly, and due to this, electrons will not move through them very well. These materials are called insulators. Rubber, plastic, cloth and dry air are good insulators. Materials that allow many electrons to flow freely are called conductors, examples are, copper, silver, aluminium, hydrochloric and sulphuric acid and saltwater.
The characteristic of materials impede flow of electric current is called resistance. Insulators have high resistance and conductors have low resistance and resistance is measured in Ohms (Ω).
How to Measure Resistance
Turn the multimeter’s knob to resistance range. Touch both RED probe and BLACK probe together, the reading on the multimeter should be 0 or near 0. Touch both ends of the material to be measured with the two probes from the multimeter. Check the reading. In the example above, the resistance for the 1K Ohm resistor is 1K.