1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Battery in parallel or series ?

  1. Apr 18, 2015 #1
    Hi fellows. Are batteries connected in parallel better than battery connected in series ? Think of two circuits , with 1 identical bulb each circuit.The first circuit is connected with a battery in series , and the battery in the second circuit will be connected in parallel (2 batteries). Which bulb is the brightest , given that the two bulbs are identical and the batteries , each has e.m.f of 1.5v. Please explain though.
  2. jcsd
  3. Apr 18, 2015 #2


    User Avatar
    Gold Member

    This sounds like a homework problem. If so, it should be posted with the template and in a homework section.
  4. Apr 18, 2015 #3


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    One option might make the bulb brighter but the other might make the bulb shine for longer. Which is "better"?
  5. Apr 18, 2015 #4
    one gives more power but less voltage, which I think is a restatement of the above post.

    "better" is subjective without a context of a specific problem.
  6. Apr 18, 2015 #5
    Current is the same throughout a series circuit, and additive in parallel. Voltage is the same throughout a parallel circuit, and additive in series. Brightness of a lightbulb is controlled by amplitude, or voltage, and the amount of time the light will burn is controlled by the current dissipated through the light and the Ah capacity of the batteries.

    BTW, both configurations have exactly the same amount of power available, according to Watt's law, P=IE.
  7. Apr 18, 2015 #6
    The problem is, in the scenario of ideal batteries (not knowing anything else that's what we can only go by), putting two batteries in parallel serves no purpose. The voltage stays the same, and combined with the resistance of the light bulb it's what determines the power transferred to the bulb, with P=V^2/R. From that standpoint the serial arrangement is the "better" since it doubles they voltage, and thus quadruples the transferred power.

    That said, the reason people put batteries in parallel is because they are never ideal. They will often have a limit to the current they can deliver, and for how long. Both of those are improved when putting several in parallel.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook