An electric cord on appliances can get warm when plugged into a wall outlet due to the flow of electric current through the cord. When an electrical appliance is connected to a power source, it completes an electrical circuit, allowing the flow of electricity from the wall outlet into the appliance and then back to the power source.
The electric current passing through the cord encounters some resistance in the cord's conductive material, usually copper or aluminum. This resistance results in the conversion of electrical energy into heat energy, according to Ohm's law, which states that the amount of heat produced in a conductor is proportional to the square of the current flowing through it and the resistance of the conductor.
When the appliance is turned on and drawing power, the electric current flows through the cord, and some of the electrical energy is converted into heat energy. This heat energy dissipates into the surrounding environment, causing the cord to warm up. The longer the cord or the higher the current drawn by the appliance, the more heat will be generated.
However, when the cord is unplugged, there is no continuous flow of current, and thus there is no electrical resistance in the cord to generate heat. Consequently, the cord remains at ambient temperature or room temperature when not connected to a power source.
It's essential to ensure that electrical cords are in good condition and that the appliances are not drawing excessive current, as overheating can be a safety concern. Using damaged cords or overloading electrical circuits can lead to dangerous situations, including the risk of fire. If you notice an electrical cord getting excessively hot, it's best to have it checked by a qualified electrician and discontinue using it until the issue is resolved.