Sorry, this may be a newbie question, but is the positive and negative terminals on a battery refer to which side has a higher potential? Or one side has positive charge and one side has a negative charge?

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  • The positive pole has a higher potential RELATIVE to the negative pole. The negative side is most often considered "Ground", at "0 volts", and the positive side is X volts ABOVE ground. – DerStrom8 Jan 6 '16 at 21:32
  • Electrons flow out the negative terminal and return to the battery via the positive terminal. – Optionparty Jan 6 '16 at 21:42

The convention for current flow was established before the electron was discovered (by J.J.Thomson in 1897). The convention is that current flows from + to -. We now know that, in fact, the mobile charges are electrons and flow from - to + but the convention has endured and we all use + to - flow but keep the reality in the back of our minds.

As is universal practice in maths, physics and general engineering, + is higher than - so we refer to the positive terminal of a battery or power supply as having higher potential. (Conventional) current will flow from the higher potential to the lower, i.e., from + to -.

schematic

simulate this circuit – Schematic created using CircuitLab

The magnitude of the current will, for a resistance load, be proportional to the voltage or potential difference between the terminals and inversely proportional to the resistance between the terminals. This is succinctly stated in Ohm's law.

$$ V = I \cdot R$$

which can be written as

$$ I = \frac {V}{R}$$

derstrom8's comment is correct. The way you need to look at it is there is a positive voltage potential at the + terminal of the battery relative to its - terminal.

To expand on that, if you had two batteries, completely disconnected, and attached one probe of a volt meter to the + terminal of one battery, and the other probe to the - terminal of the other battery, you would get ~0 volts. That is because the two batteries are not in reference to each other. You could connect just the two + terminals together, or one + terminal of one battery to the - terminal of the other battery, and nothing would happen (no current would flow), assuming the terminal of each battery was left disconnected.

This is also why if you connect the positive probe of a volt meter to the + terminal of one battery, and the negative probe to the - terminal of that same battery, you will get a positive voltage reading. If you switched the probes around, you would get a negative voltage, because you are now asking the meter to read the voltage potential of the battery as if the + terminal was ground (or 0 volts). In other words, the - terminal has a negative voltage potential in reference to the + terminal.

As far as charge goes, Optionparty's comment hits on this. The - terminal produces electrons (normally associated with a negative charge). Current flow from negative to positive (- to +) is usually referred to as Electron Current flow. However many circuits will refer to current flow as being from Positive to Negative, or Conventional Current flow.

There's a TON more theory and physics behind this question but for now, it's probably good enough to just remember that voltage is a potential between to points. If you only have a battery by itself, those points are the + and - terminals.

is the positive and negative terminals on a battery refer to which side has a higher potential?

Battery positive has a higher potential (voltage) than the negative.

Or one side has positive charge and one side has a negative charge?

Charge (in terms of simple conduction is an electron) flows from negative to positive terminals. "So many" charges passing per second is current but, due to an anomaly in the thought processes of our forebears, current was believed to flow from positive to negative - we still "conventionally" regard it being the same today even though electrons flow/pass in the opposite direction when you get down to the real physics.

  • Okay thanks, so then why when I have a negative voltage, the negative terminal has a higher potential? – Jon Sherman Jan 6 '16 at 22:03
  • @Andy: you're going to have to earn this one. ;^) – Transistor Jan 6 '16 at 22:17
  • @jonSherman the positive terminal has a higher potential compared to the negative one. – Andy aka Jan 6 '16 at 22:26

When you have 12 Volts, this means that the positive terminal of the battery is at 12 Volt higher potential as compared to its negative terminal.

If you connect the red probe of Voltmeter to the negative terminal of the battery, and the black probe of Voltmeter to its positive terminal, the voltmeter will indicate -12 Volts. Which means nothing but that the terminal of battery that is connected with the red probe is 12 volt less than that connected with the red one. So if you see this way, 12 and -12 give the same information.

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