Question

Paheli had heard that rain water is as good as distilled water. So, she collected some rain water in a clean glass tumbler and tested it using a tester. To her surprise, she found that the compass needle showed deflection. What could be the reasons?

Answer 1

Rain water contains dissolved salts. Salt in water or any kind of mineral in water makes it a good conductor of electricity and allows electric flow through it. Whereas distilled water does not contain any mineral hence it is a bad conductor of electricity.

Complete step-by-step answer:
Rain water contains dissolved salts which makes rain water a conducting solution. Whereas there are no dissolved salts present in the distilled water that’s why rain water can allow electricity to pass through it while distilled water cannot.

Additional Information:
We can make water conduct by adding electrolyte, it is a substance that when dissolved with water makes it a conducting surface.
A conducting solution is a solution that can conduct either sound, electricity or heat. Different levels of saturation defines the conductivity of a solution. When power is passed through such a conducting solution, it will result in bubbles on the surface of water. If the solution is a good conductor of electricity, then it is used as an electrolyte.
Dissolved salts refer to any minerals, salts, metals, cations or anions that are dissolved in water. Total dissolved solids (TDS) consist of inorganic salts like calcium and sulphates, and there are some small amounts of organic matter that are also dissolved in water to make it a conducting surface.
Distilled water is a type of water that is fully pure water without any minerals and salts it does not conduct electricity.

Note: The compass needle shows deflection because whenever current flows in a conducting body, it also induces a magnetic flux which is the reason why the compass could not judge the earth’s magnetic field and showed deflection.