electrical resistance electrons like any other moving body follow the path of least resistance....
TRANSCRIPT
Electrical Resistance
Electrons like any other moving body follow the path of least resistance.
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Resistance
“Electrical Friction”
Opposition to the flow of moving electrical charges
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“Resistance is Futile”?
If resistance is “electrical friction”, what benefits could resistance provide when making a circuit?
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Is resistance futile in a lightbulb?
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Symbol for Resistance
R
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Unit of Measurement
ohm
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What kind of wires would increase resistance in a circuit?
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Resistance slows down moving electrons.
When electrons slow down they convert electrical energy into light, heat and sound
What impacts resistance in a wire?
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4 things that can change resistance
The resistance in a wire depends on:
A metals structural resistance to electron flow
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The resistance in a wire depends on:
1. The type of metal in the wire
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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
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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 wireThe shorter the wire the less resistance there is
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The resistance in a wire depends on:
Thickness (Cross Sectional Area) of the wireThe wider the wire the less resistance there is
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The resistance in a wire depends on:
Temperature:The colder it is the less resistance there is
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Problem of the Day
Is resistance in a wire always bad?
bulbResistance.mp4
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Problem of the Day
Why are different wires used with different appliances?
Scroll down to the speaker playing music
http://www.stmary.ws/highschool/physics/home/notes/electricity/circuits/ResistanceWire.htm
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Ohm’s LawV= I x RVoltage (Volts)=Current (Amps) times Resistance (ohms)
electric current is directly proportional to voltage and inversely proportional to
resistance
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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?
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Current (A) Voltage (V) Resistance (Ω )
Formula Answer with Unit
Looking for thisI= ?
9V 3Ω I = (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 )
Formula Answer with Unit
Looking for thisI= ?
9V 3Ω I = (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?
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Current (A) Voltage (V) Resistance (Ω )
Formula Answer with Unit
15 A V= ? 10 V= I R 150 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?
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Current (A) Voltage (V) Resistance (Ω )
Formula Answer with Unit
15 A V= ? 8 V= I R 15 A
OHM’s Law Summary
If Voltage increases, Current _____________
If Resistance increases, Current ____________
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Ohm’s Law Summary
If Voltage increases, Current increasesMore batteries = More current
If Resistance increases, Current decreasesMore load = lower current
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Question of the Day
• What 4 things affect a circuit to give it more/less resistance?
Answer
1) Type of conductor used2) Length of wire3) Width of wire4) Temperature