Question

What is the purpose of the heavy plastic box that’s attached to your laptop charging cable? (In terms of electrical current and electricity)

Answer 1

This heavy plastic box is called Adapter. It has following functions :

Voltage Conversion

Laptop and its battery can't use the full amount of electricity provided by a regular household or office outlet, which produces 120 volts of alternating current. Inside the adapter's "line lump," a stepdown transformer reduces the strength of the current to a level the system can use. The adapter also transforms AC power into direct current. A 60-watt laptop power supply may turn household current into 16.5 V of DC electricity.

Power Compatibility

Many laptop computers use switching power supplies that can accept the 220- or 240-volt electrical power used outside the United States as well as the 120-volt standard from regular U.S. outlets. When you travel abroad with devices that include this capability, you'll need a special converter to accommodate the shape of the plug the electrical outlets use, but you won't need a power converter for the current itself.

Operating Conditions

Laptop adapters produce heat when they operate. The cord that connects the adapter to the electrical outlet on one end and to the computer on the other should stay cool. The adapter may become very warm, but it never should reach temperatures at which it becomes too hot to touch. For safe operation, set the adapter where airflow around it can help keep it cool. If it is becoming abnormally warm, verify that your battery charges correctly and replace the adapter if it continues to perform improperly.