What type of cells (primary or secondary cells) are used in an Apple Ipod and a torch respectively?
Primary cells usually means non-rechargeable. Not much use in an Ipod, to keep it small requires small cells. The cost of replacing them all the time would be too high so rechargeable secondary cells are used. The initial increased cost of these cells and a charger is lower than the running cost of constantly replacing primary cells. In a torch you can use either type of cell. However for a low use torch only used occasionally primary cells may be the better choice as primary cells hold charge (have a long shelf life) when not in use. Many secondary rechargeable cells lose their charge even when not in use. The result is that a torch with rechargeable cells in it may have no power in it when it is needed after some months of sitting on a shelf not being used. If you want it to work after a period of zero use then it probably needs to be on constant trickle charge when idle so that it works when required. This will have a high initial cost and a constant low running cost.
