Why must the end of wires be bared when it joins the pin of the plug?

The ends of wires must be bared when joining the pin of a plug to ensure a proper electrical connection. This allows the metal of the wire to make direct contact with the metal pin, facilitating efficient current flow. Bare wires also help prevent issues such as poor connectivity or overheating, which could arise from insufficient contact. Additionally, ensuring that only the necessary portion of the wire is exposed reduces the risk of accidental short circuits.