Electrical – Confusion over the power wires of USB (GND and +5v)

basicchargecurrentterminologyusb

I'm converting a battery powered device to be powered off a USB connection. I think I have everything figured out except one thing.

I understand there is a GND wire inside the USB cable for power, and also the Vbus wire (I think Vbus is also called the +5v wire). I'm lead to believe one is like the positive wire, and the other is like the negative wire. If I just look at the two wires, I would think the Black one is the negative wire, so I would hook it to the negative terminal of the formally battery powered device (after doing proper connections with a resistor of course 🙂 ). I would also think that the Red wire is the positive wire and hook it to the devices positive terminal. I would think all of that strictly based off colors and experience with other things like batteries and solar (maybe I was wrong then) .

However after doing research, the names of these two wires makes me think the opposite. The Black wire is actually Ground, which makes me think it's actually like the "return path" for the electricity (so positive). The Red wire is referred to as +5v, which makes the think that is where the "source" of electricity is coming from (so negative).

Which of these wires are the "source" (negative), and which is the "return" (positive) ? Thank You everyone!!

EDIT:
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Thank You everyone for commenting and answering! All of your replies are helping a lot!!!
I guess I always try to think about electron flow, and how electrons flows from an area that is really negative to an area that is less negative. I always
thought a batteries negative terminal was the source, and the positive terminal was the return. To hear CURRENT flows from what we call and label the positive terminal is really shocking to me and made me take a step back, yet it makes a couple other things make sense.

I find it sad that the most fundamental and basic electrical principles and ideas can actually be quite confusing.
}

Best Answer

Unfortunately, when we talk about current flow it is opposite of the direction that the electrons move. It can cause a lot of confusion.

Here is an example circuit with a battery and a lamp. We usually use the following terminology:

circuit

  • You will almost never find anyone in the industry talking about electron flow. It is always just "current", flowing from the positive ("+") terminal to the negative ("-") terminal.
  • Because of this terminology, we say that the positive terminal is the "source" of the current.
  • Voltages are measured between two points. Imagine that the battery is 1.5V. If you connect your voltmeter with it's red probe on "positive" and the black probe on "negative", it should read 1.5V. If you reverse the probes, you will see "-1.5V".
  • In an electrical schematic, the battery's negative terminal is generally referred to as "ground" or "return". All other voltages in the circuit are measured relative to this node. It is sometimes referred to as "zero volts", or "0V", to make it more intuitive.
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