Electrical Resistance Electrons like any other moving body follow the path of least resistance. Truemper 10/24/2011

Resistance “Electrical Friction” Opposition to the flow of moving electrical charges Truemper 10/24/2011

“Resistance is Futile”? If resistance is “electrical friction”, what benefits could resistance provide when making a circuit? Truemper 10/24/2011

Is resistance futile in a lightbulb? Truemper 10/24/2011

Symbol for Resistance R Truemper 10/24/2011

Unit of Measurement ohm Truemper 10/24/2011

What kind of wires would increase resistance in a circuit? Truemper 10/24/2011

Resistance slows down moving electrons. When electrons slow down they convert electrical energy into light, heat and sound What impacts resistance in a wire? Truemper 10/24/2011

4 things that can change resistance

The resistance in a wire depends on: A metals structural resistance to electron flow Truemper 10/24/2011

The resistance in a wire depends on: 1. The type of metal in the wire Truemper 10/24/2011 Which metals have low resistance? Which metals have high resistance?

The resistance in a wire depends on: 1. The type of metal in the wire Truemper 10/24/2011 Which metals have low resistance? Silver and Copper Which metals have high resistance? Nichrome and Tungsten

The resistance in a wire depends on: Length of the wire The shorter the wire the less resistance there is Truemper 10/24/2011

The resistance in a wire depends on: Thickness (Cross Sectional Area) of the wire The wider the wire the less resistance there is Truemper 10/24/2011

The resistance in a wire depends on: Temperature: The colder it is the less resistance there is Truemper 10/24/2011

Problem of the Day Is resistance in a wire always bad? bulbResistance.mp4 Truemper 10/24/2011

Problem of the Day Why are different wires used with different appliances? Scroll down to the speaker playing music ysics/home/notes/electricity/circuits/ ResistanceWire.htm Truemper 10/24/2011

Ohm’s Law V= I x R Voltage (Volts)= Current (Amps) times Resistance (ohms) electric current is directly proportional to voltage and inversely proportional to resistance Truemper 10/24/2011

Ohm’s Law Practice Problem How much current is in a circuit with a 9 V battery and a light bulb with a resistance of 3 ohms? Truemper 10/24/2011 Current (A)Voltage (V)Resistance (Ω )FormulaAnswer with Unit Looking for this I= ? 9V 3ΩI = (V/R) V divided by R

Ohm’s Law Practice Problem How much current is in a circuit with a 9 V battery and a light bulb with a resistance of 3 ohms? Truemper 10/24/2011 Current (A)Voltage (V)Resistance (Ω )FormulaAnswer with Unit Looking for this I= ? 9V 3ΩI = (V/R) V divided by R 3A

Ohm’s Law Practice Problem What is the voltage of a circuit with 15 A of current and a toaster with 10 ohms of resistance? Truemper 10/24/2011 Current (A)Voltage (V)Resistance (Ω )FormulaAnswer with Unit 15 AV= ?10V= I R150 V

Ohm’s Law Practice Problem What is the voltage of a circuit with 15 A of current and a toaster with 8 ohms of resistance? Truemper 10/24/2011 Current (A)Voltage (V)Resistance (Ω )FormulaAnswer with Unit 15 AV= ?8V= I R15 A

OHM’s Law Summary If Voltage increases, Current _____________ If Resistance increases, Current ____________ Truemper 10/24/2011

Ohm’s Law Summary If Voltage increases, Current increases More batteries = More current If Resistance increases, Current decreases More load = lower current Truemper 10/24/2011

Question of the Day What 4 things affect a circuit to give it more/less resistance?

Answer 1)Type of conductor used 2)Length of wire 3)Width of wire 4)Temperature