Benefits of earthing a metal case

• A strong current surges through earth wire because it has very low resistance

  
• Earth terminal connected to metal casing, so in such a case, the current goes through earth wire instead of causing an electric shock.

  
• Many electrical appliances, have metal cases, the earth wire creates a safe route for current to flow through if the live wire touches the casing

  
• A strong current surging through the earth wire breaks the fuse and disconnects the appliance