Battery Capacity

[Man at B&Q]

[e-mail]...

Does it take more energy to process Uranium ore than can we get from using the resulting compound in a nuclear reactor?

Does it take more energy to pick a few lumps of coal off the floor at an open cast mine than you get from burning it?

If so, these would also seem to put the laws of thermodynamics in a pickle. Due to natural processes (or divine providence in the words of the Polish guy on R4 describing his country's abundance of coal) these substances are able to yield energy to us that was locked up millenia ago.

It boils down to how much of the energy of a primary cell is put there by the processing of the constituent chemicals versus the potential energy in the raw materials. Is it all due to the processing?

MBQ

[dennis]

You should be using NiMh rechargeable in most cameras. The cameras have high discharge currents and alkalines can't keep it up.

[Man at B&Q]

You need to put new batteries in your reading glasses. He said "Lithium".

The problem in cameras is the high peak currents that can be required. These can no longer be satisfied without excessive voltage drop as the batteries discharge. A neat solution (which has been proposed if not actually implemented by some manufacturers) is to use an intermediate supercapacitor that can be charged at a lower average current and thus get longer battery life. Much the same principle as charging a capacitor to power the flash.

MBQ

[Andy Dingley]

"Hidden batteries" is one of the 4 classes of perpetual motion machine, (really works, doesn't even start to work, deceitful hidden power source, natural power source like an Atmos clock). However the electrostatic pendulum is a fairly well-known bit of honest physics demonstration kit (Glasgow University has one in an entrance hall?) but I don't think they've been "passed off" like this.