When half of the house lights go dim and half brighten after plugging in a kettle, what is the probable cause?

When half of the house lights dim and half brighten after plugging in a kettle, it indicates an issue with the electrical distribution within the house. The most probable cause is a defective neutral connection in the panelboard.

A defective neutral connection can create an imbalance in the electrical system. In a typical residential system, neutrals are used to return current to the panel from the various circuits in the house. If there is a poor or loose connection on the neutral, it can lead to erratic voltage readings across the circuits, causing half the lights to dim while the other half gets brighter. This occurs because the outlets and devices sharing that neutral will experience uneven voltage due to the disruption in current flow.

This condition can lead to potentially dangerous situations, such as overheating or electrical fires, and also may cause damage to electrical devices. Therefore, identifying and fixing the neutral connection issue is vital for both safety and functionality.

The other choices do not accurately describe the phenomenon of lights dimming and brightening in this manner. An overloaded circuit typically results in lights dimming rather than brightening, while a faulty switch or a defective capacitor would not create such a noticeable discrepancy in light brightness.