Finding conductors with a play dough circuit

We had the electric play dough out again yesterday afternoon, and I asked the small boy what conducts electricity. I wasn't sure he'd understand what I meant by 'conduct', and I was about to explain that I meant 'what electricity could travel through' when he told me it was metal. I suggested that we build a circuit to find out whether he was right.

Five minutes later, we had a circuit with a play dough car and tractor, joined by three LEDs (because one wasn't enough!), and a gap for testing different materials.  We found some things in the kitchen to see if they would conduct electricity.  We tried his cutlery (stainless steel), his brother's plastic spoon, a wooden lolly stick and some aluminium foil.

Unsurprisingly he was proved correct, with the wooden stick and the plastic fork being poor conductors. It was nice to see that the steel cutlery and the aluminium fork completed the circuit and the LEDs lit.  It wasn't at all fiddly, and just lying them across the play dough gave an instant contact.  We tried each one a few times!

Testing whether objects conduct electricity

We also accidentally asked the question 'does Mummy conduct electricity', to which the answer is yes, but not as well as a fork (the LEDs didn't light as brightly when I touched the two bits of play dough whilst positioning the plastic spoon)!  I took the opportunity to explain that the battery we were using was only 9 Volts so doesn't hurt me whereas the 230 Volt electricity in our plug sockets is dangerous. I tried to explain that voltage is about how hard the electricity is pushed around the circuit (this was the best toddler-level explanation that I could muster); the battery therefore can't push the electricity very hard, but the plug sockets can.

We had more time to experiment this time (his brother had a rare nap of longer than 10 minutes), and made a 'light switch' with the cutlery, with him shouting "on" and "off" as he enthusiastically switched the lights on and off by making and breaking the circuit.  He also wanted to put all 5 LEDs in parallel, which worked nicely too with them all shining brightly, although it was a tad tricky for his hands to get them all in the small space between the car and tractor and I had to intervene to prevent frustration getting the better of him!  We ended up with a circuit with two forks, a knife, a spoon and 5 LEDs (see picture below).

A cutlery-and-play-dough circuit