Kirchhoff's Voltage Law or Kirchhoff's Second Law states that “in any closed loop network, the total voltage around the loop is equal to the sum of all the voltage drops within the same loop” which is also equal to zero.

The unit of quantity of electricity is called the coulomb.

A coulomb is the quantity of electricity which passes any point in a circuit in 1 second when a steady current of 1 ampere is flowing. It follows that the total quantity of electricity Q, in coulombs, which passes any point in an electric circuit is given by multiplying the current I, in amperes, by the time t, in seconds.

The formula for Quantity of Electricity (Q) is = Current x Time

Battery capacity (AH) is defined as a product of the current that is drawn from the battery while the battery is able to supply the load until its voltage is dropped to lower than a certain value for each cell. Capacity of batteries usually expressed in Ampere Hour (AH).