[duncanlowe]

I remember as a youngster going on cub camp and taking a torch. Flat beast with a single battery that was a 4.5v with two contacts on the top of different lengths. But interestingly we had a box of spare bulbs at home. This used a 'prefocus' type. So I went through the box selecting the one that gave the brightest light.

Of course you can all predict the outcome: it was great when switched on briefly, but failed fairly fast when used for more than a few seconds.

As well as after the event, learning about voltage, current and power, I also recall a very brief experiment regarding what happened if you crossed the light beams. Someone involved (not me) must have had some deep theory to even try that.

At the end of the day, it didn't matter about any electrical theory or whatever, Akela confiscated all of our torches even though I protested that mine was no longer working.