You already know about the notion of electric current, the flow of positive electrical charge on a conductor of a high potential to low potential. On the battery, there are two poles of different potential. If the two poles are connected by the light through the cable, there will be a transfer of electrons from the negative to the positive pole or the case of electric current from the positive pole to the negative pole, so that the lamp can light up.
Furthermore, if the battery is used two, then the light will light up more brightly. If the battery is used three pieces, then the light is getting brighter. Why is that? This is due to the potential difference positive pole and the negative pole so that the greater the electrical charges flowing in the conductor or the electric current more and more bigger. The amount of electric current (called strong electric current) is proportional to the amount of electric charge flowing.
Strong electric current is the flow rate of the electric charge. Thus, what is meant by a strong electric current is the amount of electric charge through a conductor cross-section of each unit of time. When the amount of charge q through a conductor cross-section in time t, then I mathematically strong currents can be written as follows.
Description :
I: strong electric current (A)
q: electric charge flows (C)
t: time required (s)
Based on these equations, it can be concluded that one coulomb is an electrical charge through a point in a conductor with a fixed electric current of one ampere flowing for one second. Considering the electron charge of -1.6 × 10 -19 C, (a negative sign (-) indicates the type of negative charge), then the number of electrons (n) which resulted in a charge 1 coulomb can be calculated as follows:
1 C = n × large electron charge
1 C = n × 1.6 × 10-19 C
n = 
n = 6.25 × 10 18
So, it can be written 1 C = 6.25 × 10 18 electrons.