Mix

1. Describe the functions of circuit breakers, fuses, earthing, double insulation, and other safety devices in your home.

Circuit breakers: a circuit breakers function is to act as a fuse, which is to break a circuit path when a predetermined amount of current is passed.

Fuses: fuse boxes serve the same purpose as circuit breakers. The fuse controls the electrical current from appliances within a home.

Earthing: In electricity supply systems, an earthing system defines the electrical potential of the conductors relative to that of the Earth’s conductive surface. The choice of earthing system has implications for the safety and electromagnetic compatibility of the power supply. Note that regulations for earthing (grounding) systems vary considerably between different countries.

Double insulation: A Class II or double insulated electrical appliance is one which has been designed in such a way that it does not require a safety connection to electrical earth.

2. Discuss the dangers of electric shock from both 240V AC mains supply and various DC voltages from appliances on the muscles of the body.

When electric current passes through a person we say they experience an electric shock. The effects can range from mild discomfort to death (electrocution). The 240V electricity supply generally proves fatal. It may take as little as ~50V and current as low as ~50mA to cause death. The human body works on electricity so these signals can be disrupted if current from an external source moves through the body. For example the heart can go into ‘ventricular fibrillation’ where it quivers and does not pump properly. Electric shock can also result in violent muscular spasms and failure of the respiration system which results in death. Internal tissues and skin can also burn.

3. Complete a flow diagram to show possible stages in the transmission of electricity from power stations to consumers.