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# Ohm’s law

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### Ohm’s law

1. 1. Ohm’s Law
2. 2. The Parts• Voltage: V (volts)• Current: I (Amps)• Resistance: R (Ohms)
3. 3. Voltage: V (volts)• Measure of the “electric potential” or “potential difference”• How much “ummmph” electricity has• It is how much “push” there is behind the electrons• A 12 volt battery has more push than a 1.5 volt battery.• Car analogy: Horsepower of the engine• Water analogy: Pressure in the hose
4. 4. Current: I (Amps)• Measure of electrical flow• # of electrons per unit of time• Car analogy= Amount of cars (traffic flow)• Water Analogy= Amount of water
5. 5. Resistance: R (Ohms)• “It’s like electrical friction”(Luis P)• It is the sum of forces that slow down the electric flow• Electrons have to push theirway around the atoms in the wire• Car analogy: Road conditions and number of lanes
6. 6. Resistance• Affected by: – Thickness of wiring or circuit parts – Material of wiring or circuit – Length of wiring or circuit – Temperature – Amount of paths available
7. 7. The Formula• V=IR V I R
8. 8. Consider the equation…• If you increase the resistance, then the voltage must increase in order to have the same current. (If it’s harder to get through something, then you need more push in order to stay at same speed.)• Increasing the current will increase the voltage if resistance stays the same (more electrons have more push)
9. 9. Misconceptions• Electrons in wires move near the speed of light (T/F?) – False: They move like a train.• When batteries die, they have run out of electrons (T/F?) False: Batteries have completed their chemical reactions when they “die”
10. 10. More misconceptions• Batteries produce electrons. (T/F?) – False: Batteries give electrons a push--an energy boost—an increase in voltage.• Less electrons come out of a light bulb than those that went in. The filament uses them up.(T/F?) – False: The electrons simply lose voltage as electrical energy gets converted to light and heat
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