DEFINE 1 COULOMB ?

One coulomb is defined as that charge, which, when placed at a distance of 1 m in air or  vacuum from an equal and similar charge,  

repel it with a force of 9 x 10 power of 9 Newton

• Charge on one electron is 1.6019x10power of -19 coul.

Hence

• One coulomb is equivalent to a charge of 6.243 x 10 power of 18 electrons