Electric current

An introduction :

https://www.youtube.com/watch?v=1xPjES-sHwg

Electric currentElectric 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 the ions.

There are two fundamental quantities in electricity:

current and voltage.

Voltage is the cause and current is its effect.

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.http://ed.ted.com/lessons/electric-vocabulary#watch

For an electric current to flow, we need two things:

1) something to make the charges flow, such as abattery , a device that isable to maintain aconstant voltage betweentwo points (a potentialelectric difference ), asthe water rushes downonly if there is a differentgravitational potentialenergy between twopoints at differentheight.

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.

https://www.youtube.com/watch?v=8gvJzrjwjds

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 Amp.

So if there is a current of 5 A flowing , it means that 5 C per second are

passing a given point.

t

q

t

qi

s

CA

1

11

Part1 Charge and current : https://www.youtube.com/watch?v=KUMxSTgLSKM

Part 2 Charge and current : https://www.youtube.com/watch?v=MluOUYm8rZA

How do we define the voltage?Voltage is the potentialdifference between twopoints : it is the potentialto do work .It is measured in Volt.So if there is a voltage of 5 V, it means that 1 C hasthe potential to do 5 J ofwork.

A revision from BBC bitesizehttp://www.bbc.co.uk/bitesize/ks3/science/

energy_electricity_forces/electric_current_voltage/activity/

A test from BBC Bitesizehttp://www.bbc.co.uk/bitesize/quiz/q74171589