1. Electronics Theory Bangor High School Ali Shareef 4/7/06

2. Atoms Composed of neutrons, protons, and electrons. Protons and electrons comprise the majority of the atom’s weight. Electrons weigh virtually nothing. Protons and neutrons reside in the nucleus. Electrons orbit the nucleus.

3. Atoms Neutrons don’t have a charge. Protons have a positive charge.(+) Electrons have a negative charge. (-) Opposite charges attract. Electrons are attracted to the protons. This is the force that keeps the electrons in orbit around the neutrons.

4. Atoms The atoms tries to balance its charges and be neutral. Ex. Carbon has 6 Protons and 6 Electrons. 6 Protons = +6 Charge 6 Electrons = -6 Charge The protons’ charges cancel the electrons’ charges and you have a net charge of 0.

5. Atoms It is possible that an atom can lose an electron due to interaction by atoms of other elements. (This requires a large amount of force.) Ex: Carbon – 6 Protons and 5 Electrons 6 Protons = +6 Charge 6 Electrons = -5 Charge The protons’ charges cancel the electrons’ charges and you have a net charge of +1.

6. Atoms In order to balance itself the Carbon atom of the previous example will be actively “searching” for an electron.

7. Atoms It is possible that an atom can gain an electron due to interaction by atoms of other elements. (This requires a large amount of force.) Ex: Carbon – 6 Protons and 8 Electrons 6 Protons = +6 Charge 6 Electrons = -8 Charge The protons’ charges cancel the electrons’ charges and you have a net charge of -2.

8. Atoms Tremendous force between the 6 protons and 6 internal electrons. of a Carbon atom. The force between the 6 protons and the 2 extra electrons is much weaker. These 2 extra electrons are known as the valence electrons. If the carbon atom with a missing electrons comes near this atom, it will pull off one of the electrons of this atom.

9. Batteries Composed of two compartments filled with different chemicals. One compartment has chemicals that have excess electrons. (-) Net charge. The other compartment has chemical that don’t have enough electrons. (+) Net charge.

10. Batteries The atoms in the (+) compartment are desperate for (-) electrons in the other compartment. This force between the positive and negative compartments is known as voltage. The greater the charge difference between the two compartments the greater the voltage. When a wire is place between the (+) and the (-) terminals, the electrons rush to the (+) compartment.

11. Current The flow of electrons from the (-) compartment to the (+) compartment of the battery is called Current.

12. Electronic Circuits We can utilize this force between protons and electrons. LEDs light up when sufficient electrons pass through them. Create a circuit or “path” from the positive terminal to the negative terminal through an LED. This forces the electrons to pass through the LED to get to the (+) terminal of the battery. “You have current through the circuit.”

13. Resistance Problem: When a wire or LED is connected to a battery, all the electrons in the (-) compartment try to go to the (+) compartment all at once. This results in more current than the LED can handle and so the LED burns out.

14. Resistance Solution: Use a resistor to slow the flow of electrons. Resistor allows electrons to flow through it, but at a much slower rate. In this way, the current or the flow of electrons is at a rate that LED can handle. The LED turns on but does not burn out.

15. Measurement Units Force between (+) terminal and (-) is measured in voltage. Current is measured in Amps. Resistance is measured in Ohms.

16. Measurement Units Voltage can be measured with a voltmeter. Resistance can also be measured with a ohm-meter. Current can be measured with an am- meter. A device that can measure all these things is called a Multi-Meter.

17. Resistors Values of resistance is color coded on resistor. Black0 Brown1 Red2 Orange3 Yellow4 Green5 Blue6 Violet7 Gray8 White9

18. Calculating Resistance Values The color code can be read in the following way: (1 st Color)(2 nd Color) x 10^(3 rd Color) Example: Brown-Black-Red (1)(0) x 10^(2) = 10 x 100 = 1000 Ohms

19. Circuits A circuit diagram is called a schematic. Example: Components: B – Battery R – resistor D – Light Emitting Diode (LED) The red arrow indicates the flow of electrons in the positive convention*. Here the resistor is in “series” with the LED. (*This is reverse that of the true flow of electrons. This convention stuck thanks to Ben Franklin who thought positive charged particles traveled to the negative terminals.)

20. Demo and experiment Calculate resistor values. Experiment.