Understanding the concept of Volt and Amp supplied by USB ports of computer.

In the age of electronics, all devices feed on power supply. One of the major sources of power supply now a days is battery, which needs charging, and charging through USB (Universal Serial Bus) is very frequent. Apart from other modes of charging, we also use our laptop’s and desktop’s USB ports for charging our mobile phones or supplying power to other devices like monitor or speakers.

This blog is about sharing information on impacts of sharing power of our computer through USB Ports.

The first thing you should understand that not only volt is supplied through USB ports, but current is also supplied through USB ports. A normal USB 2.0 port supplies 5 volt(V) and 500 mili ampere(mA). And the measurement of Ampere is 1 ampere=1000 mili ampere, where in (mA) means mili ampere and (A) means ampere.

Now lets understand how much power is emitted by different USB ports.

The USB 1.x and 2.0 specifications provide a 5 V supply on a single wire to power connected USB devices.
A unit load is defined as 100 mA in USB 2.0, and 150 mA in USB 3.0. A device may draw a maximum of 5 unit loads (500 mA) from a port in USB 2.0; 6 (900 mA) in USB 3.0.

Drawing more power from the USB ports, than its capacity will heat up the chip and destroy it. Hence it is advised not to charge your mobile phones with the USB ports provided in the computers, as it will blow off the USB IC of your computer. Or at least check the power consumed by the device before plugging it to a USB port.

Source : Technical specifications are abstracted from internet

Author : Debashish Ray, Jalpaiguri, W.B., Bharat

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