Physics 12 Mr. Jean November 15th, 2011

The plan: Video clip of the day Notes on field lines which were missed Review of last day Electric Circuits Symbols The good, the bad and the ugly of circuits

AAAA!!!!! I noticed that we missed a piece during parent teacher week. On the half day I cut the lesson down to half but I didn’t start Thursday’s lesson with the piece I removed on Wednesday! My bad. Sorry!!!!

Drawing Electric Field Lines 1) The lines begin on positive charges and terminate on negative charges. 2) The number of lines drawn or net vector slope analysis emerging from or terminating on a charge is proportional to the magnitude of the charge. 3) No two field-lines ever cross in a charge-free region. (Because the tangent to the field line represents the direction of the resultant force, only one line can be at every point.) 4) The line approaches the conducting surface perpendicularly.

Field Line Density: A - has the least strong charge B - is between A and C C - has the greatest amount of charge

Field Lines in vector form:

Net vector slope analysis:

Unbalanced Charges and Fields: Let’s say that we have two positive charges with one being stronger than the other.

Unbalanced Charges and Fields: Let’s say that we have two negative charges with one being stronger than the other.

Unbalanced Charges and Fields: Let’s say that we have two charges. A weak positive charge and a stronger negative charge.

Unbalanced Charges and Fields: Let’s say that we have two charges a strong positive charge and a weaker negative charge.

Key points to field diagrams: Electric field lines always extend from a positively charged object to a negatively charged object, from a positively charged object to infinity, or from infinity to a negatively charged object. Electric field lines never cross each other. Electric field lines are most dense around objects with the greatest amount of charge. At locations where electric field lines meet the surface of an object, the lines are perpendicular to the surface.

O.k. Back on Track:

Understanding Circuit Diagrams:

Last part of symbols: Please include these last 3 items in your list of symbols.

Key points to circuit diagram: Circuit diagrams show the connections as clearly as possible with all wires drawn neatly as straight lines. The actual layout of the components is usually quite different from the circuit diagram and this can be confusing. The secret is to concentrate on the connections, not the actual positions of components.

Purpose: A circuit diagram is useful when testing a circuit and for understanding how it works. This is similar to a force diagram for understanding dynamics.

Additional Useful Keys for Success: Make sure you use the correct symbol for each component. Draw connecting wires as straight lines. Put a 'blob' ( ) at each junction between wires. Label components such as resistors and capacitors with their values listed along side or below the circuit. The positive (+) supply should be at the top and the negative (-) supply at the bottom.

Problems: 1) Draw a circuit diagram with three resistors, a battery as a power source and one push button switch. 2) Draw a circuit diagram with 4 resistors, 1 capacitor, an alternating (AC) power supply, with an led dipole controlling electric flow in the clock wise direction.

Exchange Diagrams Have your neighbour examine your diagram. Questions to consider. Does the diagram includes all of the necessary pieces? Does the diagram clearly indicate what is going on? Could you use this diagram to create the circuit above given the components in a lab?

Return diagram to neighbour: To do: Respond to the questions to consider 1) Give your neighbour constructive feedback and indication of how they are doing with their diagrams. 2) Think of ways their diagrams can be improved 3) Think of things which you will take from their diagram to improve your future drawings.

Remaining time: 1) Finish Electric Force Assignment 2) Work on project 3)