Question

An electric tester is used to check the conductivity of (a) pure water (b) vegetable oil (c) sugar solution as shown in the figure. Choose the correct statement :

• A. bulb will glow in case (a) and case (b)
• B. bulb will glow in case (b) only
• C. bulb will glow in case (b) and case (c)
• D. bulb will glow in any of the given cases

Answer 1

Answer: (B)

bulb will glow in case (b) only

Sugar readily dissolves in water, but because it does not dissociate into ions in solution, it is considered a nonelectrolyte; solutions containing glucose do not, therefore, conduct electricity.
Vegetable oil can contain some water or salts or other impurities which make them conduct electricity.
The water that we get from sources such as taps, hand pumps, wells and ponds is not pure. It may contain several salts dissolved in it. Small amounts of mineral salts are naturally present in it. This water is thus a good conductor of electricity. On the other hand, pure water is free of salts and is a poor conductor.
Hence, Only the bulb in figure b will glow.