* Reason which can cause overloading are :  *(i) When the live wire and the neutral wire come into direct contact.  *(ii) Accidental hike in the supply voltage.  *(iii) By connecting too many appliances to a single socket.*The metallic body of electric appliances is connected to the earth by means of earth wire so that any leakage of electric current is transferred to the ground. This prevents any electric shock to the user. That is why earthing of the electrical appliances is necessary.

Reasons for Overloading in an Electric Circuit:
Overloading in an electric circuit can occur due to various reasons. Here are a few common reasons for overloading in an electric circuit:

1. High Power Consumption:
When an electric circuit is used to power devices that consume a high amount of power, the circuit may become overloaded. If the circuit is not designed to handle the power requirements of the devices, the circuit may trip or even cause a fire.

2. Multiple Devices Connected to One Circuit:
If too many devices are connected to a single circuit, the circuit may become overloaded. This is because the circuit may not be able to handle the combined power requirements of all the devices.

3. Faulty Wiring:
Faulty wiring can also cause overloading in an electric circuit. This can happen when the wiring is not properly installed or if it is damaged.

4. Short Circuits:
Short circuits occur when a live wire comes into contact with a neutral or ground wire. This can cause a sudden surge in current, which can overload the circuit.

Why is Earthing Necessary for Appliances with Metallic Body?
Earthing is an important safety feature for appliances with metallic bodies. Here's why:

1. Protection from Electric Shock:
When an appliance with a metallic body is connected to the electrical supply, there is a risk of electric shock if there is a fault in the appliance or the wiring. Earthing provides a safe path for the electric current to flow to the ground, preventing electric shock.

2. Protection from Fire:
Earthing also helps to protect against fire caused by electrical faults. If there is a fault in the appliance or wiring, the current can flow to the ground without causing a spark or fire.

3. Protection of Appliance:
Earthing also protects the appliance itself. If there is a fault in the appliance or wiring, the current can flow to the ground through the earthing wire, preventing damage to the appliance.

4. Compliance with Safety Standards:
Finally, earthing is a legal requirement in many countries to ensure compliance with safety standards. Appliances with metallic bodies must be earthed to ensure the safety of users.