Bright and dim play dough lights

We had another play with our battery, LEDs and play dough (following on from yesterday's electric play dough).

The small boy wanted all the LEDs in a line (i.e. in series), and with our two colours of dough, so I helped him to build it. I was informed that my job was making balls of play dough as he was keen to put the LEDs in himself.  He also enjoyed explaining to me that the long leg had to point the right way because they were one way streets, so he'd clearly been listening yesterday!

We connected the battery and ended up with a series circuit with 5 LEDs. Nothing happened. He told me he'd broken it and looked a little worried! I thought there was probably too much resistance so I got him to try moving the play dough attached to one terminal of the battery to light one LED and it lit brightly! He then tried two and they both lit, but not as brightly. Then he tried 3 (a bit dimmer) and 4 (barely visible) before testing all 5 again. He did this several times over and saw it was the same each time. 

We talked about how the electricity was struggling to get around the long circuit because it was difficult and there were lots of obstacles for it to pass - not a brilliant analogy for resistance but the best I could muster without thinking it through beforehand.  Any better ideas for explaining this to a  toddler are very welcome, please leave a comment if you have any thoughts!

Testing whether we could make a single LED light

I attempted a video so you can see a little better how it worked for us (no sound because it had a little voice saying "mama" repeatedly then shrieking...).  I'm not sure whether videos display well on here, so please do leave a message if you have any problems watching it.

Again, our playing was somewhat curtailed by the attention span of his brother! I'm sure we will be trying electric play dough again soon...