 When electric charges flow they experience opposition or resistance which reduces the amount of energy they have  Greater resistance -> greater amount of energy each charge has to give up

Filament – high resistance Therefore, lot’s of energy taken from each electron and turned into light Wire – low resistance Therefore, little energy lost – turned mainly into heat

 The amount of energy (voltage) required to push electrons (current) through a conductor

 German Physicist Georg Ohm determined that for a given conductor, the ratio of voltage to current (V/I) is constant  We call this constant resistance (Measured in Ohms -  ) = ConstantResistance

 Relates voltage, current and resistance  Note: E stands for electric potential (commonly known as voltage)

 Electrical Insultator ◦ Prevents the transfer of electric charges ◦ Ex: Air, glass, rubber, paper  Electrical conductor ◦ Low resistance which allows electric charges to flow easily ◦ Ex: copper

 A single cell is set-up in a circuit with a switch and a resistor. For the resistor, a voltmeter is set-up and it measures 1.3V and an ammeter is set-up and it measures 3.5A. a) Draw the circuit with the correct set- up of a voltmeter and ammeter b) Calculate the resistance of the resistor

 If a resistor has a resistance of 1000  and the current is 2.0A. What will be the voltage drop across the resistor?

 Pg 330 # 1a  Pg 332 # 1, 3-5  Pg 331 # 5ab,7,8

 Series ◦ Only one path for current to flow

 Parallel ◦ More than one path for current to take

 We have four tools we can use to analyze circuits: ◦ Kirchoff’s Current Law (KCL) ◦ Kirchoff’s Voltage Law (KVL) ◦ Ohm’s Law ◦ Equivalent Resistance (Series and Parallel)

 At any junction (Point) in the circuit, the current going in equals the current going out  At a point, I in = I out  Note: In any series circuit, every point has the same current

 In any complete path in a circuit, the sum of voltage rises (sources) is equal to the sum of voltage drops (loads)  For a path, V rises = V drops

 Pg 337 # 1-3  Pg 343 # 1, 2, 4

 If you have many resistors (or loads) in a circuit, finding the equivalent resistance allows you to replace multiple resistors with a single resistor  This allows easier analysis of circuits

The easiest way to put this formula into a calculator is to use your inverse button (x -1 )

 Pg 339 # 4-6  Pg 340 # 7