Presentation on theme: "View Vow How many electrons go past a point every second in a wire if the current is 12 Amps?"— Presentation transcript:
View Vow How many electrons go past a point every second in a wire if the current is 12 Amps?
Objectives Understand that current tells us how much charge (think moving electrons! – but more to come on this) moves past a certain point every second. We all know “Resistance is futile”…but what is resistance when we are talking about Current?
Homework Castle Learning – Current and Resistance
Test Corrections today post and tomorrow. I do have a meeting today but I will be in here so feel free to come today for corrections. Please look over, ask questions, check the scoring and then return to your mailbox.
R A Resistance Factors R ρ R L R Temp. To build an “ideal” conductor with the smallest possible resistance you would select one that is: LOW RESISTIVITY, SHORT, WIDE, COLD
Determine the resistance of a 1.0 meter long copper wire with a cross-sectional area of 0.01 meter 2. Example #1 R = ρL / A R = (1.72 x 10 -8 Ω·m)(1.0 m) / (0.01 m 2 ) R = 1.72 x 10 -6 Ω
A piece of wire that has a length of 5.0 x 10 7 meters and a cross-sectional area of 0.025 meter 2 has a resistance of 31.8 ohms. –What is the composition of this wire? Example #2 R = ρL / A ρ = RA / L ρ = (31.8 Ω)(0.025 m 2 ) / (5.0 x 10 7 m) ρ = 1.59 x 10 -8 Ω·m