Fruit batteries

Discussion in 'Supporting Physics' started by clairelucas, Jan 23, 2018.

  1. We have just done fruit batteries, and although it worked well with multimeters, showing increasing pd with series of fruit 'cells', we never managed to light a bulb. I used a 1.5v mes bulb, as it was the smallest we have. What was I doing wrong?
    Idiot questions/answers always appreciated...
  2. karen b

    karen b COMMITTEE

    What voltage were you measuring?
  3. Hi Claire. You're 1.5 bulb will work fine. All you need is more fruit. In the past I've used 6 Lemons to get a decent glow. How much have you used?
    Have you checked whether the bulb is OK? Happy New Year.:);)
  4. Dod


    Need to series a few to overcome resistance of bulb, a multimeter draws negligible current.
  5. With 1-5 fruits we were getting 0.8-2.4v and tried multiple bulbs in case blown...Have now just checked bulb- barely glows on 1.5v battery but bright with 2..
  6. 8 satsumas, 4.3V but only 0.3mA on multimeter.. guess the resistance is a problem. will try afresh with fresh lemons. But not this week..
    Last edited: Jan 23, 2018
    GeorgetheScienceTech likes this.
  7. Nick Mitchener

    Nick Mitchener COMMITTEE

    you don't need more fruit though, you can do one lemon with a number of electrodes wired together, red LEDs are relatively easy to light, and if you get the ones with a built in joule thief it will look very successful.
    Sarah Benham and clairelucas like this.
  8. I think that the Satsuma may be the trouble. The more acidic the fruit the better.:D:D
    clairelucas likes this.
  9. 10 Fresh (Premium Sicilian) Lemons in series has the capability of powering 1-or 2 carriages of a Train Set.:D:D:D
    clairelucas likes this.
  10. I have to disagree with you Nick- the number of Lemons and the acidity of the Lemons is important. Potato batteries function in a slightly different way-they contain small amounts of Phosphoric acid.:)
  11. Nick Mitchener

    Nick Mitchener COMMITTEE

    Feel free to disagree George, but you are wrong, you can make a battery, rather than a cell, with one lemon. I did not say acidity was unimportant, but that you can use a single fruit with multiple electrodes to increase the output.
  12. the electrodes make a difference as well, have seen some books saying two copper ones...o_O
  13. The only problem with multiple electrodes is that power drain occurs more quickly. This is why my Lemons/Potatoes are all wired in series.:)
  14. Nick Mitchener

    Nick Mitchener COMMITTEE

    That's a different issue, we aren't usually looking for a long term power supply but something that will be easily made and prove a point.

    I've seen a single lemon used to ignite wire wool.
    GeorgetheScienceTech likes this.
  15. I presumed 2 of the same metal would just not do anything.. misprint?
  16. I, however, am looking for a long term power supply to move my 2 carriages of the Train Set.:D:D
  17. PhysicsSimon

    PhysicsSimon COMMITTEE

    I think the problem with the mes bulb is that the current will be too low - which is why LED's are a better option (can be full brightness on 200mA) but even so you may need a number of electrode pairs in series to get a decent glow (whether all stuck in the same lemon or different ones I'll leave to you!)