Lecture Text, Electricity

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This course is a Virtual Laboratory tutorial in electronics.  Over the last decade,  I have produced a set of free online circuit simulations and animations that constitute a interactive virtual laboratory for students studying electronics or preparing for an IT career .  My virtual interactive circuit troubleshooting exercises cover only a small sample of circuits covered in must texts or college courses. This selection of circuits ranges from simple resistive circuits thru advanced operational amplifiers, digital circuits and computers .   I believe that those who  master troubleshooting my narrow range of virtual circuits or systems will develop the skills necessary to troubleshoot a wide range of circuits and systems that they will be confronted with now and in the future.  I feel quite certain that someone who could not perform the majority of my virtual troubleshooting exercises would be in need of further training in order to become a competent electronics troubleshooter.  This person could benefit from my free virtual laboratory course. 
                                                                               

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Lecture Text, Electricity

Electricity Lecture

Review main points:  This should be a review for those who have taken High school Physics.  For those of you who have not had High school physics, I recommend you download and study my e-book Force Field Visualized

1. Current flows in the direction of E field.  That is it flows from positive to negative potential.

2. Current normally flows in the direction of arrows on transistors and diode symbols.

3. Current in wire and resistors is due solely to electron flow.

4. Current in transistor and diodes is due to hole flow. Holes are positively charged molecules.

5. Positive charged particles flow in the direction of current and E fields.

6. Negative charged particles flow in opposite direction of current or E fields.

7. The electromagnetic force of a battery induces positive ions to move to the positive plate of a battery. 

8. The electromagnetic force of a battery induces negative ions to move to the negative plate of a battery.

9. Holes (positively charged molecules) in silicon crystal lattice carry charge in semiconductors and move in direction of current. Current is in the direction of E field. Current direction is indicated by direction of arrow on transistor or diode.

10.About direction of current.

Case 1: At this very moment a beam of electrons is traveling from the gun in the back or neck of the CRT directly towards your face (pretend you are looking at Cathode Ray Tube [CRT] if you have a flat screen monitor).  Luckily for you the beam  strikes the phosphorous coated surface of the CRT prior to striking you.  Now make a  fist with your left hand directly in front of your face.  Now point your thump directly in the direction of your face.  Your thump is now pointing in the same direction as the electron beam.  This electron beam produces a magnetic flux that curls about beam in the direction of the fingers on your left hand.  This is a physical fact of nature not a rule.  

Case 2: Next, I want you to imagine that your CRT was actually an ion propulsion engine and instead of electrons coming straight at you there were positive ions coming straight at you.  Now make a  fist with your right hand directly in front of your face.  Now point your thump directly in the direction of your face.  Your thump is now pointing in the same direction as the positive ion beam.  This ion beam produces a magnetic flux that curls about the beam in the direction of the fingers on your right hand.  This is a physical fact of nature not a rule.  

The Right Hand Rule states that when you point your thump in the direction of electrostatic field (E) that is driving  the beam, the curl of your fingers indicates the direction of the Magnetic H field.  Note that conventional current also flows in the direction of electrostatic field.  Thus, when you point your thump in the direction of conventional current, your fingers curl in the direction of the magnetic field.  The right hand rule is the only rule you will need to remember.  What about the case of the electrons hitting the CRT.  Just remember that conventional current is flowing in the opposite direction of the electrons, then the right hand rule will give you the correct direction of the curl for the CRT magnetic field.  Thus, you only need the Right Hand rule to determine the direction of the magnetic field curl.   This rule could be used by an electronic technician, if he or she were trying to wind a coil or was attempting to measure current flow with a compass.  In the real world of  technicians, coils and transformers are labeled, and meters are used to measure current.  The remainder of my lectures will focus on teaching you how to troubleshoot and actually allow you to self test your ability using my simulations.   I also lack the ability to program a Wizard with artificial intelligence to answer your questions. So, please email me relevant questions so that I can add a F A Q page to this site.

  BilPat4342@AOL.com

 

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Last modified: Monday July 07, 2014.