What is considered to be extra-low voltage (ELV)?

Extra-low voltage (ELV) refers to voltage levels that are considered safe for human contact and are unlikely to cause electric shock under normal conditions. The standard definition for ELV is that it encompasses any voltage that is under 50 volts for alternating current (AC) or under 120 volts for direct current (DC).

Option B correctly identifies extra-low voltage as being under 50V AC or under 120V DC, which aligns with recognized safety guidelines and standards in electrical work. This range is established to limit the risk of electrical shock and ensure safety when dealing with electrical installations and equipment.

The other options describe voltage ranges that are beyond the threshold of what is classified as extra-low voltage, which increases the risk of electric shock and necessitates greater caution and protective measures. Consequently, understanding the classification of voltages is essential for electrical safety and compliance with regulations.