ELEMENTS OF ELECTRICAL PHYSICS DYNAMIC ELECTRICITY

SUBCOURSE 0337 ARMY INTELLIGENCE CENTER OF ELECTRICAL PHYSICS ELECTRICITY OF ELECTRICAL PHYSICS ELECTRICITY Number IT 0337 A ARMY INTELLIGENCE CENTER HUACHUCA AZ 85613 6000 Credit Hours Date December 1995 OVERVIEW subcourse is designed to teach you the physical properties of electricity in motion the three necessary for electron movement and the units of measurement assigned to these this subcourse is taken for review you should previously have completed subcourses IT 0332 IT 0336 subcourse replaces SA 0707 LEARNING OBJECTIVE will be able to identify the conditions under which electricity will flow identify definitions of and statements about current flow electromotive force and and identify the units of measurement for these values correct and incorrect statements and definitions and this text demonstrate competency of this task you must achieve a minimum of 70 on subcourse examination 0337 OF CONTENTS Overview of Electrical Physics Dynamic frames that are not identified number are the Practice and answers 0337 OF ELECTRICAL PHYSICS ELECTRICITY DESCRIPTION this lesson you will learn the physical properties of electricity in motion the three conditions for electron movement and the units of measurement assigned to these necessities LEARNING OBJECTIVE will be able to identify the conditions under which electricity will flow identify definitions of and statements about current f 3w electromotive force and and identify the units of measurement for these values correct and incorrect statements and definitions and this text demonstrate competency of this task you must achieve a minimum of 70 on subcourse examination 0337 now we have been considering static electricity or electricity at rest This type of electricity no practical use because it does not provide a continuous source of electrons To get our T V radios and yes even our radar sets to operate we must have a continuous source of electrons the electrons must be in motion In other words we must have electricity in action This electricity action is known as Dynamic Electricity have dynamic electricity that is electricity in motion we must be able to get the electrons to To accomplish this three conditions are necessary 1 a supply of electrons ready and able to 2 a path through which the electrons can move and 3 some kind of force to push them the path we will consider how each of these needs is satisfied Then we will move on to consider the in which these three necessities are measured the rate at which the electrons move how a given path or conductor allows electrons to move and how much force is produced by a of electricity course electrons have to come from atoms Some atoms seem to have more electrons than others Which of these substances would be a good source for supplying a continuous of electrons 1 4 2B 1 8 6A 1 10 8B 1 12 10A ANSWER The ping pong balls jam up Page 1 10 8B isn the answer we wanted Perhaps we better describe the setup a little more tube is just big enough for the ping pong balls to pass through There nothing to stop the from moving along if pushed The tube can contain only the number of balls shown Thus if ball is pushed in at one end the rest are forced to move along one space The ball at the far is going to be unlucky there isn space in the tube to which it can move to page 1 10 8B for another answer 0337 ANSWER Page 1 8 6B conductor to another An electron moves with the speed of light from one end of a you trying to get through this at the speed of light If you are slow down and make sure absorbed what you being told electron DOES NOT move from one end of a conductor to the other at thousands of miles per But an electron enters the end of a conductor what happens is this Its dielectric field forces an off a nearby atom ionizing the atom Our No 1 electron then joins the atom it has ionized the atom to electrical neutrality but leaving displaced electron No 2 without a home until it its turn ionizes another atom and starts the whole process over again by displacing electron No 3 effect travels down the line with a chain reaction crash whiz crash And it is this effect that travels the conductor at the speed of light 186,000 miles per second so that it is felt almost at the far end of the conductor But remember that the individual electron finished its almost before it was begun It does not whisk in a straight line from end to end in the return to Page 1 8 6B and select the correct answer ANSWER 1 3 1A would be a good source for creating a continuous flow of needs rethinking amber rod you recall was used in our earlier experiments as the source of a negative The negative charge was placed on the rod by rubbing the rod with a woolen cloth Amber has property of taking electrons from another substance It has none it can give up easily until it has some Thus it is hardly a good source for creating a continuous flow of electrons to Page 1 3 1A for another answer 0337 ANSWER Page 1 10 8B the other end ping pong ball pops out the other end By inserting a ping pong ball at one end of the filled tube we have made another come out of the sort happens when an electron is made to pass into a conductor It exerts a force on the electron nearest it and this force is passed on through a kind of chain reaction so an electron another electron not the first one pops out at the far end conductor then must be able both to give and to take electrons easily It must have a good of electrons that will easily pass back and forth between its atoms so that the chain reaction can take place electrons that can be made to move in this way are called free electrons They are used to up electric current which is what we call the directed flow of electrons that word directed In materials that have many free electrons the electrons normally move and forth between the atoms But this is not called current since it is a random motion not aimed in one direction you could see an atom under a microscope where would you expect to find the free electrons the outer shell an inner shell the nucleus all of the above 1 8 6B 1 10 8A 1 12 10B 1 14 12A 0337 ANSWER False Page 1 8 6B are right It is not true that an electron moves from one end of an electrical conductor to the with the speed of light The entering electron finds a home in the atom it ionizes There it stays another electron comes along to knock it off course if an electrical current is continuing to flow that electron is likely to be knocked off pretty Nevertheless an electron moves through a conductor much more slowly than the chain it sets off The chain reaction is what we know as an electric current we think of current in a length of conductor then there is electron transfer along this length at the of light But the important point is that the electrons pushed out at one end of the conductor not the same ones pushed in at the other end The entering electrons set up the chain reaction passes bump bumpety clang bump through the conductor at fantastic speed to send the electrons on their way say it again to make it perfectly clear The current moves through a conductor with the speed light It might take an electron several months to get through a mile of wire this statement true or false At normal temperatures there is no movement of electrons in a until a push is applied 1 9 7A 1 11 9A 0337 are correct ANSWER Page 1 11 9A you connect the two charged plates with a copper wire the charges far as you gone There more to it than this however a question of what happens to make the charges disappear The left hand plate begins with a of 4 positive unit charges The right hand plate has a charge of 4 negative unit charges The plate in other words is short of electrons to the extent of 4 unit charges the right hand plate a surplus of electrons to the extent of 4 unit charges they are conne