Electric Current Circuits Resistance and Ohms law MHR

Electric Current, Circuits, Resistance and Ohm’s law MHR pg. 619 -632

What is Electric Current? An electric current is: the movement of electrons ( think of a water current- movement of water) These electrons carry energy ( in volts) and can transfer their energy to a load such as a light bulb

Formula for Current I = Q / Δt Where I = current ( amps) Q = amount of charge ( coulombs) Δt = change in time ( seconds)

Problem #1: Cell phone chargers What is the current travelling through a cell phone charger when 0. 20 m. C of electrons pass a point in 0. 75 min? Answer: 4. 4 x 10 -6 A

How do you measure electric current? Review. What is going on with the diagram below? Where would you put the ammeter? Follow the symbols pg. 619 in your text book How bright are the two light bulbs?

Analyse this circuit: The ammeter goes ______the first light bulb. How bright are the two light bulbs?

How much energy does each light bulb absorb? Measure the voltage ( change in energy) across each light bulb in the circuit below: The light bulb that is brighter has more or less energy?

How much energy does each light bulb absorb? Measure the voltage ( change in energy) across each light bulb in the circuit below: How bright are the light bulbs? How much energy does each light bulb require?

Electrical Resistance (R) Electrical Resistance: is a measure of how difficult it is for an electrical current to travel through a material High resistance materials: do not allow an electric current to pass through ( example: plastic) Low resistance materials: allow electric current to pass through ( example: copper)

Resistor An electrical device that has a specific resistance The units for resistor is ohms or Ώ

Ohm’s Law If you were to graph the amount of energy the electrons transfer to a load (V) vs the flow of electrons that pass through a load (I), the graph would look like this:

So what do we do with straight lines? Take their slope!!!!

Ohm’s Law Where : R= resistance ( Ώ) V = potential difference ( V) I = current ( A)

Your Turn… Read pg. 622 -625 MHR pg. 632 # 21 -26 ( blue background) MHR pg. 632 # 1, 2 ( yellow background)