Tallor

Meet Tallor, a stopwatch on a wire who counts the charge flowing past each second.

Electric current is the rate at which charge flows. One ampere means one coulomb of charge passing a point every second, so the charge delivered is just the current multiplied by the time.

A current of 2.0 A for 60 s moves 2.0 × 60 = 120 C. Each electron carries 1.602 × 10⁻¹⁹ C, so one coulomb is about 6.24 × 10¹⁸ electrons, and 120 C is about 7.5 × 10²⁰ electrons.

Battery capacity is often given in milliampere-hours, which is a measure of charge. A 3000 mAh phone battery can deliver 3.0 A for one hour, which is 3.0 × 3600 = 10 800 C.

Although so much charge flows, the electrons themselves drift slowly through a wire, often less than a millimetre per second. The signal to move travels far faster, because the whole wire is already full of electrons that start moving almost together. By convention, current is drawn flowing from positive to negative, the opposite way to the electrons.