# Q = I × t : Quantity of Charge (Electricity) Calculations Tutorial

## Key Concepts

- A galvanic cell (voltaic cell) produces a flow of electrons.
This flow of electrons is called an electric current.

Current is given the symbol I and is measured in units of amperes (amps, A). - The amount of charge passing a point in an electric circuit depends on the electric current and the time the current is allowed to flow for.
The amount of charge is given the symbol Q and is measured in units of coulombs (C).

- The quantity of charge (or electricity) contained in a current running for a specified time can be calculated:
Q = I × t

Q = quantity of charge (electricity) in coulombs (C)

I = current in amperes (amps, A)

t = time (seconds) - This equation can be rearranged to calculate the electric current given quantity of charge (electricity) and time:
I = Q ÷ t

- This equation can be rearranged to calculate the time taken given the quantity of charge (electricity) and the electric current:
t = Q ÷ I

- This equation can be used to determine the quantity of charge, electric current, or length of time required to run an electrolysis experiment such as:
(i) for electroplating

Example from industry: electrorefining of copper(ii) electrolysis of molten salts to extract a metal

Example from industry: extraction of aluminium from bauxite

Example from industry: extraction of sodium from molten soduim chloride(iii) electrolysis of aqueous solutions to extract an element:

Example from industry: electrowinning of copper