A base with a light bulb and two long prongs sits above a beaker partially filled with liquid; the prongs extend into the liquid. To the right, 2 wires extend from a source labeled Power; 1 attaches to the base and 1 to the right-hand prong. On the left, 2 wires are attached to the terminals of a battery, with 1 wire attached to the base and 1 to the left-hand prong. The third test you read about uses the apparatus shown above to test for conductivity of electricity. If the bulb lights up, then the substance dissolved in the water is likely ✔ ionic.covalent.