The charges on a proton and an electron are equal in magnitude but opposite in sign. One coulomb of charge is equal to 6.242 x 1018 elementary charges and one. elementary charge is equal to 1.6 x 10 19 C. 7. Electric current is defined as the rate at which electric charges flow through a conductor. 8. In symbols, it is given as: electric current where Q charge t time 9. The SI unit for current is ampere (A), where 10. The current that flows through a conductor is said to be one ampere if one coulomb of charge flows past the conductor in one second.