1 Electronics Nature of Electricity Copyright © Texas Education Agency, All rights reserved.

2 Specific Objectives State the law of charges Explain the law of charges using several examples Explain what electric current, voltage, and resistance mean Describe electrical work Describe differences between conductors, insulators, and semiconductors Describe where conductors, insulators, and semiconductors are used Copyright © Texas Education Agency, All rights reserved.

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4 Law of Charges This is also called Coulombs Law. Charge is a fundamental property of electrons and protons. Charged particles have an invisible force field around them, which interact according to their respective charge. Positive or negative Like charges repel each other while unlike charges attract each other. Copyright © Texas Education Agency, All rights reserved.

5 Law of Electrical Charges A. Like charges repel Example: Electrons repel electrons B. Unlike charges attract Example: Protons attract electrons Copyright © Texas Education Agency, All rights reserved.

6 Demonstration of Coulombs Law Requirements One piece of fur One vulcanite rod Two pith balls hanging from a beam Directions 1. Negatively charge the vulcanite rod with the piece of fur. 2. Bring the rod close to one hanging pith ball. 3. Observe that the ball is first attracted to the rod because of unlike charges. When the ball touches the rod, it is immediately repelled. Copyright © Texas Education Agency, All rights reserved.

7 Coulomb’s Law (continued) 4. Continue to attempt to touch the pith ball with the vulcanite rod. 5. Recharge the vulcanite rod and touch it to the second pith ball. You now have two negatively charged pith balls. 6. Bring the two pith balls near each other. Do your observations match? 7. Charge up the glass rod by rubbing it with a piece of silk. Touch the glass rod to one of the pith balls. Leave the other negatively charged. Copyright © Texas Education Agency, All rights reserved.

8 Coulomb’s Law (continued) Question Why has the pith ball acted this way? Answer Like poles repel each other; unlike poles attract each other. Copyright © Texas Education Agency, All rights reserved.

What is Electricity? Electricity is a general term that describes the type of energy source. Other energy sources include chemical, heat, mechanical, or light energy. Each of these energy sources can be converted into electrical energy. Electrical energy can be converted back into any of these types of energy to do work. Electricity is a convenient way to deliver energy for general use. 9 Copyright © Texas Education Agency, All rights reserved.

10 Important Electrical Terms Current is the movement of electrons in a conductor. (Measured in amps) Voltage is the force behind the electrons. It moves them along the conductor resulting in current. (Measured in volts) Resistance is the quality of an electric circuit that opposes the flow of the current through it. (A measurement of the opposition to current flow in ohms [Ω]) Copyright © Texas Education Agency, All rights reserved.

What is Voltage? A difference in potential Always relative – compares something to something else Measurement made between two things or places An invisible force that acts on charged particles Created by a separation and collection of opposite charges Electrons separated from a nucleus 11 Copyright © Texas Education Agency, All rights reserved.

What is Current? The movement of electrons directed by an external force The force can be an electrical force Voltage The force between charged particles Described by Coulombs Law The force can be created by magnetism A conductor moving through a magnetic field Generator action 12 Copyright © Texas Education Agency, All rights reserved.

13 Random Drift of Electrons The movement of an electron occurring naturally with no controlling force applied. This movement is random. This means that there is no collective or net movement of electrons. Heat is a primary energy source. Creates free electrons in a conductor, but does not direct their movement. Even when no controlling or directing force is present, electrons can move from the orbit of one atom to the orbit of another. Copyright © Texas Education Agency, All rights reserved.

14 AC and DC Current AC = Alternating Current A current of electrons that moves first in one direction and then in the other. Created by a generator DC = Direct Current A flow of electrons in one direction. Created by a battery  Both forms are used to create work.  AC is more efficient to send over long distances because the voltage can be stepped up with a transformer. Copyright © Texas Education Agency, All rights reserved.

Electrical Work Work is defined as force times distance. Something has to move for work to be done. Electrons are the “something” that moves to create electrical work. Current is the measurement for the amount of movement by electrons. More current equals more work. 15 Copyright © Texas Education Agency, All rights reserved.

16 Conductor, Insulator, Semiconductor A conductor of electricity is anything that permits the free flow of electrons. A good conductor has many free electrons. An insulator is a material that will not permit the free flow of electrons. An insulator has no free electrons. An insulator is a poor conductor of electricity. A semiconductor is a material that limits the flow of free electrons. A semiconductor has few free electrons. Copyright © Texas Education Agency, All rights reserved.

Conductors are used to deliver voltage where it is needed (like an electrical outlet). Insulators are used to keep voltage from going where it is not wanted (for safety and protection). Semiconductors are used to control the amount and direction of current flow. 17 Copyright © Texas Education Agency, All rights reserved. Conductor, Insulator, Semiconductor (continued)

18 ConductorsInsulatorsSemiconductors CopperBakeliteSelenium IronGlassSilicon SteelMicaGermanium AluminumPorcelainCuprous Oxide SilverAirLead Sulfide TinDry WoodSilicon Carbide Damp EarthSandGallium Arsenide Salt WaterRubberGallium Phosphide Conductors, Insulators, and Semiconductors (continued) Copyright © Texas Education Agency, All rights reserved.