In an electrolysis setup, which observation confirms that an electric current is passing through the solution?

• A. The bulb will light.
• B. The solution changes color everywhere.
• C. No observable change occurs.
• D. Only the temperature rises without any visual change.

Answer: (A)

When an electrolyte conducts electricity, ions move to the electrodes and carry charge through the solution, completing the electrical circuit. If the current is passing, the circuit is closed and the lamp in the setup will light. That visible glow is a straightforward indication that electrons are flowing from the power source, through the wires, into the solution, and back again.

Other observations aren’t as reliable indicators. A color change throughout the solution would require a bulk chemical change, which isn’t a typical feature of basic electrolysis. No observable change could happen if the reaction is slow or the setup isn’t drawing enough current. A temperature rise might occur due to resistance, but it’s not a clear or consistent sign of current flow in a simple demonstration.