I would like to state that I'm a beginner in learning electronics by reading my first book on electronics I'm lost and would like some help. I even included an image that would hopefully help my case.

By learning series and parallel circuit. What confuses me if we have a battery plus terminal and minus and one light bulb wire coming from positive terminal of battery connects to positive terminal on light bulb and negative terminal of battery connects to negative terminal of light bulb. Why does in series circuit if we have for example 3 lights bulbs and one battery wire connects from negative terminal of light bulb to positive terminal of another light bulb I don't get it. In parallel circuit wire coming from battery connects to positive terminal of battery and negative to negative even if we have 3 light bulbs. But in series circuit light bulbs are connected with wire from negative terminal of battery to positive terminal of battery. I found out its because of light bulbs have no polarity. But LED lights have polarity and they are still connected the same way. I don't get it. To makes things easier I put some markings on image.

example from the booktmR.png

  • \$\begingroup\$ because the negative side of the LED is connected to the negative side of the battery? \$\endgroup\$ Commented Apr 27, 2023 at 18:53
  • \$\begingroup\$ @user253751 has it right. That said, you're probably lucky, because hooking it up the other way probably would have burned out your LEDs, or at least one of them, with too much current. \$\endgroup\$ Commented Apr 27, 2023 at 20:18
  • \$\begingroup\$ @user253751 The long LED leg is always positive. you can write + on the short leg, but that doesn't make it positive. \$\endgroup\$ Commented Apr 27, 2023 at 21:16
  • \$\begingroup\$ Your LED circuit would just fry the LEDs. \$\endgroup\$
    – Hearth
    Commented Apr 28, 2023 at 3:42
  • \$\begingroup\$ The circuit just needs a series resistor, unless the LEDs have one built-in. \$\endgroup\$
    – PStechPaul
    Commented Apr 28, 2023 at 3:52

2 Answers 2


'+' and '-' are relative designations. In your picture with the LEDs, the '+' terminal of the red LED is at the same potential as the '+' terminal of the battery (because they are connected together.) The '-' terminal of the red LED and the '+' terminal of the amber LED are at a lower potential. The '-' terminal of the amber LED and the '+' terminal of the green LED are lower still, and so on until you get to the '-' terminal of the battery which is the lowest potential of all.

If we put a ground symbol anywhere in that circuit, then the circuit node with the ground symbol is arbitrarily designated as 0V, and we can assign voltage numbers to other nodes to show how many volts above (positive) or below (negative) the node is with respect to ground.

Often, when there is a ground symbol, it is attached to the lowest voltage in the circuit (the '-' terminal of the battery in this case) so that all of the other voltages will come out as positive numbers.


A main characteristic of a series circuit is that the current has a single path through all components in the circuit. In your series circuit, if one lamp is burned out, none of the lamps will light. With three identical lamps in the circuit, each lamp will only see one third of the battery voltage.

In a parallel circuit the current has multiple paths throug the circuit. Each lamp is independent - if one lamp burns out, the rest are not affected. All lamps will see the full battery voltage.


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