Many gadgets run on rechargeable batteries. The alternating current (AC) adapter that plugs into the wall to run your cell phone or electric razor may be warm to the touch. If it's excessively hot, that usually spells trouble.
An AC adapter is a palm-sized plastic box that plugs into a household electric outlet. A cable connected to the box carries low-voltage DC. A round metal power connector at the cable's end plugs into your device.
Inside the adapter, a circuit called a regulator holds the DC voltage steady. Normally, it becomes moderately warm.
If your gadget is working hard, it gets more current from the adapter. The adapter will get warmer. If overloaded, it may become hot.
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A problem in the adapter's circuits may cause it to run abnormally hot. If it becomes painfully hot to touch, grip it with a dry rag and remove it from the wall outlet.
Unless you have a strong background in electronics, using an appliance with an AC adapter that didn't come with it is not a good idea. The voltage, polarity or current may be incorrect, leading to overheating and damage.