1. Technologies can be used to transfer and control electricity
Unit D Section 2.0
Technologies can be used to transfer and control electricity

2. 2.1 – Controlling the Flow of Electrical Current
Electrical current flows through circuits
The amount of current that can flow through a circuit is limited by the conductive properties of the components in the circuit

4. Conductors and Insulators
In conductors, electrons can move easily because they are not tightly bound to the nuclei of the atoms
In insulators, the electrons cannot move easily

6. Superconductors
A superconductor is a material that have no resistance to electron flow
Many materials are superconductive at very low temperatures

7. Using Conductors, Resistors & Insulators
Resistance is a measure of how difficult it is for electrons to flow
Resistance is measured in ohms (Ω)
Resistors are parts of a circuit that provide high resistance to reduce the amount of current flowing through the circuit
For any given voltage, more current flows through a resistor with a LOW resistance than one through with a HIGH resistance

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9. Devices that use Resistors
The more resistance a substance has, the more the substance gains energy from each electron passing through it.
The energy gained is radiated to its surroundings as either heat or light
Some examples of devices that use resistors are:

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11. Switches and Variable Resistors
Switches create a break in the circuit that interrupts current flow, therefore controlling the flow of current in the circuit
A variable resistor is another type of control
These resistors (also known a rheostats) allow you to adjust the amount of current flowing through a circuit, rather than simply turning it on or off
This can be done through control knobs or pedals

13. Topic 2.2 Modeling and Measuring Electricity

14. Electrical Charge Electrical charge is measured in Coulombs
This is named after Charles A. Coulomb
1 coloumb = 6.25 billion billion electrons

15. 2.2 – Modeling and Measuring Electricity
Voltage is a measure of how much potential energy each electron that flows through a circuit possesses
Voltage is related to both current and resistance in circuits

17. Ohm’s Law
In 1826, Georg Ohm determined through experiments that voltage (V), current (I) and resistance (R) are mathematically related:
Resistance is measured in ohms (Ω)

18. Ohm’s Law states that, as long as temperature remains constant:
The resistance of a conductor remains constant
The current is directly proportional to the voltage applied

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21. Applying Ohm’s Law

22. 2.3 – Analyzing and Building Circuits
Circuit diagrams or schematics are representations of a circuit that is built
Recall that all circuits require four components:

24. Parallel and Series Circuits
Circuits can be divided into two general types: parallel and series
These circuit types are defined by the number of branches that are present in the circuit

25. Series Circuits
Definition: the current passes through each bulb in turn – there is only one pathway
Diagram:

26. Parallel Circuits
Definition: have a separate path for each section of the circuit
Diagram

27. Effects of Multiple Paths in Parallel Circuits
In parallel circuits, adding more resistors in circuits actually will reduce the overall resistance of the circuit
As well, the voltage change in each branch is equal

28. Applications of Parallel and Series Circuits
Parallel circuits are more commonly used in devices than series circuits
Imagine what would occur if your house used series circuits instead of a number of parallel circuits…

29. Transistors
In tiny consumer electronics, transistors are used instead of conventional switches
Transistors are made of three layers of silicon sandwiched together
These transistors have no moving parts and operate on digital code running through the middle layer of the transistor to control the movement of current through a circuit

30. Microcircuits Are also called integrated circuits
Are made up of microscopic transistors and resistors
It is a circuit on an extremely small scale