Physics 12 Mr. Jean April 3th, 2014

The plan: Video clip of the day Review Assignment Questions Volts Ohm’s Law Current

Electric Potential Energy: WSVh4https:// WSVh4

Ohm’s Law: V = IR V = Potential difference in volts (v) I = Electric current in amperes (A) R = Resistance in ohms (Ω) 1A * 1Ω = 1V

Unit of resistance: One ohm is defined as the amount of electric resistance that will allow one ampere of current to move through the resistor when a potential difference of one volt is applied across the resistor.

Example: What is the resistance if a battery with 9.0V of potential difference causes a current of 0.45A to pass through a resistor?

Electric Current: I = the current in Amperes (A) q = the amount of charge in Coulombs (C) ∆t = the change in time in seconds (s) Note: One coulomb per second is equivalent to one ampere.

Flow of Current: Electrons flow from the negative terminal to the positive terminal. –When electricity was first discovered they didn't really have a way of telling which way it was flowing so they made a guess. –As it turned out, the guess was wrong. When an electron moves from one position to another it leaves a "hole" behind. Another electron flows in and fills this hole, leaving its own hole further down the line. So in practice although electricity can be considered as a stream of electrons flowing from negative to positive, it can be equally considered as a stream of "holes" flowing from positive to negative.

Conventional vs. Electronic Current: Conventional current flows from positive to negative. Electronic current which is the flow of electrons flows from negative to positive. This is because on negative terminal, there are more electrons. In the symbol for a battery, longer line shows positive terminal whereas shorter line represents the negative terminal.