Which is a common conductor?

• A. Salt water
• B. Copper
• C. Plastic
• D. Glass

Answer: (A)

Electric current flows when there are charged particles free to move. Metals carry current with free electrons, while solutions carry current with ions that move when an electric field is applied.

Salt water is a common conductor because dissolving salts like sodium chloride creates ions (Na+ and Cl−) in the water. These ions move in response to an electric field and carry charge, allowing electricity to pass through the solution. The more dissolved salt, the more ions, and the higher the conductivity.

In contrast, plastic and glass are poor conductors because their structures trap charge carriers; their electrons aren’t free to move, so they act as insulators. Copper is also a good conductor, but in everyday contexts involving liquids, the charged ions in salt water provide a very practical and common path for conduction.