Why is the flash drive not charging, but the phone is charging from the PC?

Question

USB

At the institute, professor asked the question: Why does not it charge when a USB flash drive is connected to a PC, but if the phone is connected to a PC, does it charge? I assumed that it was the lack of a battery on the USB flash drive, but this answer turned out to be wrong

Answer 1

Probably, the teacher wanted you to get acquainted with The Basics of USB Battery Charging

Answer 2

Well, if the answer is wrong with the battery, then you can suggest the option of not having a charge controller, but it will not be far from the option with the battery.
Perhaps he wants you to tell us about the types of USB connectors - they are Type A and Type B.
Type A is an active device that can power others (computer, splitter). Type B is a passive, consuming device (printer, scanner, hard drive, your flash drive).
Also pay attention to the USB pinout - in the case of 4 lines there is + 5V D- D + and GND. D is for data transmission, and 5V and ground are constant voltage and zero. There may be a question about it.

Answer 3

Childish question. That is, you need to answer so that the child understands.
We simplify.
The child only charges the phone.
Watching cartoons from a flash drive.
It turns out there are two types of use.
data and charge.
Power supplies do not work with data.
A typical port in which a flash drive will be read is designed for consumption of no more than 0.5A. Even less on TV.
Phones are charged with currents up to 2A. From 0.5 they can, but for a long time. Because they are smart and know how to adapt.
Charge is the accumulation of energy. There is nowhere to put it in a flash drive