1. Electric current
An introduction :

2. Electric current
Electric current is an ordered motion of charge carriers
between two points having
different electric potential ( = voltage) .
In a metal wire the charge carriers are the conduction electrons,
while in a liquid or in a gas they are ions or , or by both ions and electrons such as in a plasma
There are two fundamental quantities in electricity:
current and voltage.
Voltage is the cause and current is its effect.

3. We are going to study the current in metals.
The conventional direction of the current, for historical reasons,
is defined as opposite to the direction of motion of the electrons.

4. For an electric current to flow, we need two things:
1) something to make the charges flow, such as a battery , a device that is able to maintain a constant voltage between two points (a potential electric difference ), as the water rushes down only if there is a different gravitational potential energy between two points at different height.

5. For an electric current to flow, we need two things:
2) a complete path for the current to flow in. This is called an electric circuit.

7. How do we define the rate of current?
Current is the number of Coulombs that passes a point during a second. We measure it in Amps. So if there is a current of 5 A flowing , it means that 5 C per second are passing a given point.

8. Part1 Charge and current : https://www. youtube. com/watch
Part1 Charge and current : Part 2 Charge and current :

9. How do we define the voltage?
Voltage is the potential difference between two points : it is the potential to do work . It is measured in Volt. So if there is a voltage of 5 V, it means that 1 C has the potential to do 5 J of work.

10. A revision from BBC bitesize http://www. bbc. co

11. A test from BBC Bitesize http://www.bbc.co.uk/bitesize/quiz/q74171589