1. Electric circuits
Charge and Current

2. Electric Circuits
To make an electric circuit, we have to get electrons to travel in a continuous circle through a device that can change their energy. For example, a light bulb is something that can turn the moving (kinetic) energy of the electrons into light.

3. Components of a Circuit
Circuits can be very complicated with many devices designed to control and direct the flow of elelctrons but a simple circuit only requires the following
Power Source – Something that creates a source of free electrons (e.g. a battery)
Wires – To conduct the electrons around the circuit
Load – A device that converts the energy of electrons into something useful (e.g. a light bulb or heating coil)
Switch – Something that allows us to break the circuit and stop the flow of electrons

4. Components of a circuit

5. Drawing Circuits Power Source Wires Load Switch
When electricians plan electric circuits they use symbols to represent the parts
Power Source
Wires
Load
Switch

6. Types of circuits
Some circuits are very simple and some are very complicated with many loads, switches wires and power sources.
But circuits can be divided into three basic types:
Series Circuit – All the electrons take the exact same path through the circuit

7. Types of circuits
Parallel Circuit – All the electrons start at the same place and finish at the same place but can take different paths

8. Types of circuits
3. Combination Circuits – Has both series and parallel components.

9. Electric Charge
Charge (q) is a measurement of the number of electrons. Electrons are very small so it is impossible to count the exact number that are going through a circuit. Instead, scientists (and electricians) measure charge in Coulombs. Think of a Coulomb as a huge pile of electrons.
1 Coulomb = × 1018 electrons

10. Electric current Electrons move quickly through a circuit
Current (I) is a measurement of the speed that the electrons are moving. Current is measured in Amperes.
Think of current as the number of electrons that pass a certain point in the circuit each second
Current = Charge/Time or I = q/t
1 Ampere = 1 Coulomb/s

11. Learning Check
If 12 Coulombs of charge pass through a point in a circuit every 5 seconds, what is the current?

12. Learning check
Since I = q/t
I = 12/5 = 2.4 Amperes or 2.4 A

13. Exploration activity
All circuit components are at the back of the room
Instructions:
Work in Groups of 3-4
Take the following back to your workspace
Two batteries and cases
10 wires
4 lights (you can take motors too)
4 switches
Begin by making a simple circuit and turning it on
Look at page 554 question #4 and try to make each circuit that is described.