Charged up
In my last post I wrote about an invention that produces light from the potential energy stored in a bag of rocks. Apparently, what a lot of people want to know is whether it will charge up a mobile phone. Different phones use different batteries but let’s take an AA battery, how much energy is stored in it? The EMF of a battery is the energy converted to other forms per unit charge so the total energy contained in the battery = EMF x charge it contains. The current flowing from a battery is the charge flowing per unit time. If current I flows in time t the charge flowing from the battery = It. So current x time (Amp hour) is the charge contained in the battery, if this is multiplied by the EMF then we can calculate the energy stored. Batteries are rated as to how many Amp hours they are, an alkaline long life AA battery is rated as 1.15AHh which is 2.12x3600 As or Coulombs. The EMF of an AA battery is 1.225V so the energy stored = 1.225x2.12x3600 = 9350J. If the gravity lamp was used to charge this battery the rocks would have to be lifted 52 times.