§11.4 Charge and Current

• Science
• Upper Secondary (Key Stage 4)

§11.4 Charge and Current

Science - TTO2

Learning Objects

• State that an electric current is due to a flow of charge. 
  
• Recall that electric current is measured in Amperes (A). 
• Describe the use of an ammeter. 
• State that charge is measured in coulombs. 
  
• Describe that a current is a rate of flow of charge. 
  
• Do calculations with the formula: I = Q / t. 
  

Time for a video!

Watch the video about Charge and Current on the next slide.

Electric Charge

• An electric current is due to a flow of charge
  
• Looking at the model of an atom: Electrons are the only charged particles that are able to move. 
• Therefore: An electric current is a flow of electrons.

Electric Charge

• The thing with electrons is: There are SO many!
• That is why we don't measure charge in the number of electrons, but in Coulombs. 
• Think of it as a BIG bag of electrons      -->
  

Electric Current

When electric charge starts moving, we call it an electric current. 

Therefore: 

"An electric current is due to a flow of electric charge"

Electric Current

• To measure the current we use an Ammeter. 
  
• It simply 'counts' how many Coulombs pass by a point in the circuit every second. 
  
• The unit of Electric Current is called Ampere (A).

 

Electric Current

The ammeter has to measure the amount of charge that flows through the lightbulb. 

Therefore, it has to be in the same circuit as the lightbulb and the battery.

We say the components are in series, because the same amount of charge flows by each component every second. 

Electric Current

Now that we know that Electric Charge is measured in Coulombs, and Electric Current is the amount of Coulombs passing through a point per second... It's time to put this in a formula:

We know that:

 1 Ampere = 1 Coulomb per second

Therefore: I = Q / t

See the next slide for the eqation.

Time for some practice:

• Read p. 160-161 (TB) 
  
• Do Summary Questions p. 161 (TB) 
  
• Do workbook exercises p. 82 (WB) 
  
• Check all your answers from Ch. 11 with the answer model. 
  

When water starts flowing, we call it a current. An Electric Current is also a flow of something...

What flows in an Electric Current?

1. Drops of electricity
2. Electrons
3. Amperes
4. Protons

What is the unit of Electric Charge?

1. Charge (Q)
2. Ampere (A)
3. Coulombs (Q)
4. Coulombs (C)

Where do we use an Ammeter for?

1. To measure the amount of charge flowing through a point every second
2. To measure how hot a light bulb gets
3. It supplies energy for the light bulb to shine