Noughts & Crosses

• Science
• Middelbare school
• vwo
• Leerjaar 2

Electric current is the flow of electrons through a complete circuit of conductors. It is used to power everything from our lights to our trains.

Electricity is a flow of charge 

Electricity is a flow of charge 

Properties of Electric Charge

Charge can neither be created nor be annihilated, but can be transfered from one body to another.

Opposite charges attract each other,Like charges repel each other.

Conventional current and electron flow

• Electron current flows from the negative terminal to the positive terminal of the battery. 
• The conventional current flows from the positive terminal of the battery to the negative terminal.

Electric Charge

• The thing with electrons is: There are SO many!

• We don't measure charge in the number of electrons, but in batches.

• One such batch is one coulomb.

What is current?

You already know:

• Electricity is a flow of charge.

This can be

Quantified

First, pause the video and try to answer it for yourself. After that continue playing the video.

What is current?

You already know:

• Electricity is a flow of charge.

This can be

Quantified

The amount of coulomb flowing through an electric circuit per second — Coulomb/second

First, pause the video and try to answer it for yourself. After that continue playing the video.

What is current?

• Symbol: I
  
• Unit: Ampere (A)
• Formula:                           Current = Charge / time

Charge — Coulombs (C)

time — seconds (s)

I=​t​​Q​​

The amount of coulomb flowing through an electric circuit per second —  Coulomb/second

First, pause the video and try to answer it for yourself. After that continue playing the video.

Units of current

1. Ampere or amp (symbol: A) is the unit of electrical current.

2. A milliampere (often called "milliamp") is a unit of electric current . The symbol for milliampere is mA. 

1 milliampère = 0,001 A

Resistors

We use resistors to control the flow of current from a voltage source, like a battery.

They resist the flow of charge, they are poor conductors.

The value of resistor is measured in ohms and represented by the Greek letter capital omega.

Before we go on, let's talk about resistors.

Resistance is calculated in Ohms (Ω)

We can see that each resistor has 4 lines painted on it. These lines are simply telling us their resistance.

• 1st line - 1st digit of our amount
• 2nd line - 2nd digit of our amount
• 3rd line - the multiplier for our first two digits
• 4th line - the tolerence of the resistor i.e. its percentage error

Let's try one out!

What is the resistance of this Diode?

• Answer:
  470Ω ±5%

LED

Light Emitting Diode