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Electrical Resistance Electrons like any other moving body follow the path of least resistance. Truemper 2016 Which road would you want to travel on? Truemper 2016 Which road would you want to travel on? Electrons in a circuit are like cars on a road – what happens when electrons encounter a traffic problem? Truemper 2016 Resistance “Electrical Friction” Opposition to the flow of moving electrical charges Truemper 2016 “Resistance is Futile”? If resistance is “electrical friction”, what benefits could resistance provide when making a circuit? Truemper 2016 Problem of the Day Is resistance in a wire always bad? Resistance in a light bulb Truemper 2016 Is resistance futile in a lightbulb? Truemper 2016 Truemper 2016 Symbol for Resistance R Truemper 2016 Unit of Measurement ohm Truemper 2016 What kind of wires would increase resistance in a circuit? Truemper 2016 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 2016 4 things that can change resistance Truemper 2016 The resistance in a wire depends on: A metals structural resistance to electron flow Truemper 2016 The resistance in a wire depends on: 1. The type of metal in the wire Which metals have low resistance? Which metals have high resistance? Truemper 2016 The resistance in a wire depends on: 1. The type of metal in the wire Which metals have low resistance? Silver and Copper Which metals have high resistance? Nichrome and Tungsten Truemper 2016 The resistance in a wire depends on: Length of the wire The shorter the wire the less resistance there is Truemper 2016 The resistance in a wire depends on: Thickness (Cross Sectional Area) of the wire The wider the wire the less resistance there is Truemper 2016 The resistance in a wire depends on: Temperature: The colder it is the less resistance there is Truemper 2016 Problem of the Day Why are different wires used with different appliances? Truemper 2016 Truemper 2016 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 2016 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? Current (A) Voltage (V) Resistance (Ω ) Formula Looking for this I= ? 9V 3Ω Truemper 2016 I = (V/R) V divided by R Answer with Unit 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? Current (A) Voltage (V) Resistance (Ω ) Formula Answer with Unit Looking for this I= ? 9V 3Ω 3A Truemper 2016 I = (V/R) V divided by R 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? Current (A) Voltage (V) Resistance (Ω ) Formula Answer with Unit 15 A V= ? 10 150 V Truemper 2016 V= I R OHM’s Law Summary If Voltage increases, Current _____________ If Resistance increases, Current ____________ Truemper 2016 Ohm’s Law Summary If Voltage increases, Current increases More batteries = More current If Resistance increases, Current decreases More load = lower current Truemper 2016 Question of the Day • What 4 things affect a circuit to give it more/less resistance? Truemper 2016 Question of the Day • What 4 things affect a circuit to give it more/less resistance? 1) 2) 3) 4) Type of conductor used Length of wire Width of wire Temperature Truemper 2016 Question of the Day • What 4 things would produce the most resistance in a circuit? Truemper 2016 Question of the Day • What 4 things affect a circuit to give it more/less resistance? 1) 2) 3) 4) Use Tungsten Long wire Thin of wire Warm Temperature Truemper 2016
