Connecting multiple high-power appliances to a single socket.
Explanation
In domestic electric circuits, appliances are connected in parallel. Overloading occurs when the total current drawn through a circuit exceeds the current-carrying capacity of the wires. This generates excessive heat, which can damage insulation and cause fires.
Detailed Analysis:
- The use of a fuse wire with a high melting point. is Incorrect: Using a fuse wire with a high melting point is a safety hazard because it may fail to melt and break the circuit during a fault. However, the fuse itself does not cause the condition of overloading; it merely fails to prevent the damage resulting from it.
- Connecting multiple high-power appliances to a single socket. is Correct: When multiple high-power appliances (such as heaters, irons, or geysers) are connected to a single socket, they draw a combined current that may exceed the rated capacity of the circuit or the socket. Since domestic circuits are parallel, adding more appliances decreases the equivalent resistance and increases the total current, leading to overloading.
- A sudden drop in the supply voltage. is Incorrect: A sudden drop in supply voltage generally reduces the current flowing through resistive appliances (according to Ohm’s Law, \(I = V/R\)). Therefore, it does not typically cause overloading.
- The presence of moisture in the switchboard. is Incorrect: The presence of moisture in a switchboard can lead to a short circuit (direct contact between live and neutral wires), which causes an abrupt surge in current. While this results in high current, the term "overloading" is specifically used to describe a situation where the load (connected appliances) exceeds the circuit's rating, whereas "short circuit" refers to a fault condition.
Key Takeaway:
Overloading in domestic circuits is primarily caused by connecting too many appliances to a single socket or an accidental hike in supply voltage, both of which cause the current flow to exceed the safety limit of the wiring.