How can you identify appliances with double insulation and what does it mean for earthing?

• A. They do not have any symbol.
• B. They carry a symbol indicating low voltage.
• C. They have enhanced insulation in the plug and cord.
• D. They carry a double square symbol; do not require an earth connection.

Answer: (D)

The key idea is recognizing how double insulation is indicated and what it means for grounding. Double insulation means the appliance is built with two layers of insulation (or a single layer with reinforced insulation) so a user is protected from electric shock without needing a protective earth connection. The telltale sign is the double square symbol (two squares, one inside the other) on the device. When you see this symbol, the device is Class II and does not require an earth connection.

So, the do-not-rely-on-earth implication is that you can use the appliance with a two-wire plug rather than a three-wire plug with an earth pin. The other options don’t correctly identify the distinguishing symbol or the concept: it’s not about a low-voltage indicator, and insulation in the plug and cord alone isn’t the defining feature of double insulation.